For a small introduction, I am known as ai darkfluid and am a Viktor main with ~460K mastery on him and have been playing League of Legends for about 2 and a half years. This is a guide meant for anyone, from players who want to pick up Viktor, to people who know Viktor very well, as this "guide" is meant to give each player who reads it insight on the champion, match-ups and itemization. I have many differing opinions on which example build can work in which situations, so I highly suggest sitting down and at least skim through this guide to understand which build to go if you are new, and see the match-ups and itemization if you still have the time.

Additionally, here are some terms you may want to know:
CS - Minion score (Creep score)
AA - Auto attack (Basic attack)
CD - Cooldown
CDR - Cooldown reduction
AP - Ability Power
AD - Attack damage
MS - Movement Spee
CC - Crowd Control (Slows, movement/action restriction)

1.0 Introduction
1.1 ToC
2.0 Viktor's Kit
2.1 Viktor's Kit (Tips and usage)
3.0 Champ Select
3.1 Viktor Counters
3.2 Rune Choice
3.3 Planning build paths
3.4 Summoner Spells
4.0 Laning
4.1 Roams
4.2 Farming
4.3 Ganks
4.4 Responding to collapses
5.0 Teamfight notes
6.0 Itemization
7.0 Win conditions
7.1 Kill Pressure
7.2 Objective Control
8.0 Final Notes
8.1 Weaknesses
8.2 Conclusion

Ability Breakdown

Firstly, Viktor has his Q - Siphon Power:

This is a strong early trading tool, having the most power at level one, as it grants Viktor a shield on cast that scales with AP and level. This allows you to out-trade most match-ups level one. Augmented, it grants boosted movements speed and regardless will give an enhanced auto attack that scales with AP and behaves like a laser. This will be strongest in lane due to the nature of trading and because Viktor's next auto attack behaving like a laser, it bypasses Yasuo's Windwall and has a faster animation when comparing Viktor's normal auto attack.

TL;DR Viktor's Q is a projectile that deals magic damage. It grants him a shield and when augmented bonus movement speed on cast. His next AA will deal bonus magic.

Second, his W - Gravity Field

Viktor places a circular field onto the rift and after a 0.75 second delay,for each half-second a non-friendly entity is inside, they are given a stack that slows them for an amount, each stack increasing that amount. Once the entity reaches 3 stacks, they are stunned for 1.5 seconds. After augmenting, all of Viktor's non-ultimate damaging abilities (Q,E) will slow targets by 20%. Enemies cannot be stunned twice in the same cast and are not effected after they are stunned. This is mostly used for either a zoning tool, or AoE hard crowd control at choke points.

TL;DR Viktor's W places a trap that, after a short delay, will slow enemies and eventually stun them if they persist in the trap. After augment, Viktor's Q and E will slow enemies hit.

Third, he has his E - Death Ray

This is the ability that you are going to spam the most in teamfights and post-lane. On the player's command, Viktor will shoot a single line that deal damage to whatever comes into contact. This line can go over walls, travels a set distance from the initial spot cast and can be placed in any direction. The ability acts in quick cast as if it had quick cast with indicator and after augmented, follows the line after a short delay with a burst of damage.

TL;DR Viktor's E acts like a line that deals damage. It can be placed over any object and after augment, follows the path with a second burst after a short delay.

Finally, Viktor has his ultimate, Chaos Storm

Viktor's ultimate allows him to send a singularity that generates a circle of death that continually deals damage at 0.5 second intervals and initial damage on cast. This additionally silences enemies under it when the ability is first cast and can be redirected when re-casting the ability. If the singularity is cast on an enemy champion, the singularity will follow them. Finally, the singularity moves slower the further it is from Viktor.

TL;DR Viktor's R places a circle of AoE damage that can move. It follows whoever the spell is casted on and can be re-casted on anything. His ult silences whoever it is initially cast on and deals damage over time.

Now that you have a basic understanding of the kit you have to work with, this section will focus on how to most effectively use Viktor's kit.

Abilities

Viktor - Positioning King If you position wrong, you cry Running Away: When running from an enemy chasing you such as Renekton or Garen who can easily run you over you essentially have two choices. In such a situation, you can use either Siphon Power or Death Ray. After W Gravity Field augment, both basic damage spells induce slows, however the key to deciding which spell to use is based off distance. Watch the following clip for an example. Play Video As shown, I got an eventual kill on Garen by spacing, abusing the Siphon Power movement speed, and the slows from Death Ray and Siphon Power. This kill was definitely calculated and I definitely knew Garen's Demacian Justice cd, and definitely did not luck out, but what's important to take from this clip is that Viktor's Q - Siphon Power forces Viktor to stop in place during the cast, while his E - Death Ray does not. Use your own judgement on which spells to use while keeping this in mind while being chased down by Mr. Unkillable 6 item Dr. Mundo. Understanding Choke Points Firstly, what is a choke point? A choke point is essentially wherever one player, or multiple must path through to get to an end destination. These are essentially found at any entrance to an objective and are at areas that are, when obstructed, forces them to either punish themselves by pathing through that area if possible, or delaying their push by choosing an alternate path. I have labelled some choke points that one can use, so try them on the rift and see how opponents scramble to react, either forcing flashes, delaying pushed onto objectives, or getting some montage Q>E>R setup. Using your ult key Your ult silences people. This means that it cancels all casts, and for a very short duration, they cannot cast spells or abilities. This is very strong and feels underrated in most situations. You can singlehandedly stop Xerath Rite of the Arcane, living Karthus Requiem, and Fiddlesticks Crowstorm. You can chain Chaos Storm and Gravity Field together to devastate someone who relies on abilities that involve both wind-up and movement. If you know how much time, for example, Crowstorm requires before Fiddlesticks blinks, you can place gravity field, wait for ~1 second so 2 stacks are applied, then cast Chaos Storm on Fiddlesticks to stop his channel. This would nearly ensure Fiddlesticks can't get out of Gravity Field and force him into a stun, where you can likely burst him for a free kill. Upgrade Path: Death Ray > Siphon Power > Gravity Field > Chaos Storm

Who am I against?

This is a question that may come into your mind and should factor into if you should lock in Viktor. Look to the bans and see which is most likely a mid ban. After, search for the most-likely mid match-up based from either the mid-tab or general knowledge.
Prepare to lane against champions such as Diana, Yasuo, Zed, Annie, Talon and Ekko. Oh, and Veigar. He can one shot anyone for some reason.

Look for the threats section for notes on specific match-ups. All these match-ups are based off my own opinion and heavily depends on the player. Tips are given per each match-up in their notes.

This should help determine general threats.

Runes can be game changing. I have put differing example runepages that you can follow, however this chapter will be focusing on when to use which specific rune.

Sorcery

Summon Aery: Summon Aery is the standard rune for Viktor. It supplies extra poke damage at a near consistent rate and applies a shield if taken with heal whenever heal is used. Use either this rune or Arcane Comet if you believe you need to win lane through poking. Arcane Comet: Arcane Comet is a rune that acts similarly to Aery, however it has more damage and a longer cooldown. This is slightly more orientated towards team fights, as it has AoE damage, however in lane it has around the same impact as Aery, albeit with less consistency due to the longer cooldown. If you think comet will specifically win you a fight, sometimes it has damage that cannot be ignored, but it overall feels underwhelming. Due to Augment - Magnetize ( Gravity Field augment) enemies hit by either Death Ray or Siphon Power will be slowed, and are almost guaranteed to get hit by comet. Phase Rush: Phase Rush can be taken into an enemy team comp that mostly relies on close-mid range champions. It grants a large burst of movement speed and slow resist and for Viktor is a means to survive longer to spam more spells. This can be triggered easily from either a flurry of Siphon Power > Death Ray > AA, or Siphon Power > Chaos Storm > Death Ray. Either combo can be used to engage or disengage if you choose to incorporate Gravity Field. Examples of these champions are Syndra, Yasuo, Rammus, and Kayn. Manaflow Band: Manaflow Band is the only rune that should be taken in this row for sorcery. This is due to its effect outweighing both Nimbus Cloak and Nullifying Orb at almost every situation in nearly every stage of the game. Nimbus Cloak is something similar to a niche pick. Bonus movement speed is always welcomed, however Celerity can be taken without as much drawback from the lack of mana and mana sustain that would exist if Nimbus Cloak were to be taken. Transcendence: Transcendence grants 10% bonus cdr and converts exceeding cdr into adaptive force, which grants bonus stats depending on what you build (AD/AP). Celerity: Celerity grants an excessive amount of movement speed, which as Viktor, you will love. I personally prefer Celerity to Transcendence as it encourages survivability and potential to play in riskier situations than you normally would. Scorch: Scorch Allows your spells to burn the enemy for small amounts of damage. Before 20 minutes, it should outdamage Gathering Storm. Gathering Storm: Gathering Storm Grants Viktor adaptive stats over time and is one of the best late-game runes as it scales with time.

Domination

Electrocute: Use Electrocute when playing into a comp that is heavily composed of close - mid range champions when you need extra kill pressure. Like Phase Rush, Electrocute can be triggered with a plethora of combos, but Electrocute can be easily triggered level one by AA > Siphon Power > AA. Dark Harvest: Dark Harvest triggers when hitting a target with less than half health. This can be triggered in fights more than once, as long as Viktor gets a takedown (kill or assist). After takedown, Dark Harvest goes resets its cooldown to 1.5 seconds and has infinite scaling. While this sounds tempting, I believe Electrocute always finds more success as its unlikely the game will drag to the point where Dark Harvest will outscale Electrocute. However, if you think the game will drag on, or you can trigger Dark Harvest during the lane phase frequently, so mid - late game it still damage. Cheap Shot: Cheap Shot has some strong synergy due to it's low cooldown of 4 seconds, and Viktor's W Gravity Field augment inducting slow on targets when hit by Siphon Power or Death Ray. Once a target is slowed and Viktor hits them with any damage, bonus true damage will be inflicted on them. Taste of Blood: Taste of Blood is a very strong lane rune, as it heals Viktor once damaging the enemy laner. This can come from an AA, or a spell. Zombie Ward/Ghost Poro/Eyeball Collection: Zombie Ward Ghost Poro Eyeball Collection all eventually give equivalent adaptive force, which equals 30AP. On Viktor, the norm was to take Eyeball Collection while taking domination due to it previously giving more AP than the others in its row, however the vision Ghost Poro provides leads me to believe that Ghost Poro is the better rune for Viktor. Essentially, Zombie Ward summons an ally ward on enemy ward takedown, Ghost Poro summons a ball of fluff to give ally vision when your wards expire, and Eyeball Collection gives AP on takedown. Since they all eventually give the same AP, the vision Ghost Poro provides feels to outweigh the other options. Ravenous Hunter: Ravenous Hunter is the best sustain rune in the game, only sometimes being outshined by conqueror. Its sustain makes it the only choice as without it, everything hurts a lot more, in or out of lane.

Inspiration

Unsealed Spellbook: Unsealed Spellbook is a rune that, for Viktor helps increase late-game survivability. I recommend using Flash Ghost when using unsealed spellbook, as they are the most potent and effective during team fights, and the summoner spell restriction Unsealed Spellbook gives to unequipped summoners feels too long for the consistent team fights in the late game. First swap should either be Barrier, Ignite, or Teleport to either increase lane time (farming and experience gain) or apply pressure, either through Ignite's bonus damage, or teleport's global applications. Clarity is also available for free bonus in-lane mana (not recommended to take into the late-game unless your build does not build mana), and Smite can be taken during the mid-game for faster objective clears. Magical Footwear: Magical Footwear is the rune you want to take if you want some bonus mid-late game mobility. You should get it ~1/2 through lane phase depending on how many takedowns you get in-lane. Magical Footwear grants free boots with +10 movement speed after 12 minutes, but with each kill, that time lowers. Remember, more mobility = better kiting = profit(?) Perfect Timing: Perfect Timing is a free Stopwatch. Takedowns heavily reduce the initial cooldown of 14 minutes, and can be built into Zhonya's Hourglass. I personally don't take Perfect Timing, however Viktor does get some benefits from this, and as he is a squishy mage, it's a fine choice of rune. Future's Market: Future's Market is my favourite rune, as you can go into debt. If you absolutely want to buy Hex Core MK-1 on your first back, instead of flexing into a second Doran's Ring, Amplifying Tome, Catalyst of Aeons, or Tear of the Goddess, this may be the rune for you. Go into virtual debt, for science! (50 gold fee is applied for every use.) Minion Dematerializer: This probably used to be my favourite inspiration rune for Viktor during season 8 and 9. After a nerf, which reduced how many of the items you receive, it cut the power of Minion Dematerializer enough to make me stop taking it, however it still has its original uses. You deal more damage to minions, so your Death Ray is more liable to one-shot non-cannon waves, and the item itself can help you shove in the current wave so you can look to recall or roam to top, bot, or secure deep vision. Biscuit Delivery: Biscuit Delivery is a very strong lane-sustain rune, as it recovers resources (mana and health) based off of missing resources. It also grants bonus mana on use, per biscuit, however you can only use biscuits 3 times per game. Cosmic Insight: Cosmic Insight grants 5% cdr for EVERYTHING. It's. Very. Strong. However, it is situational, as other runes in this row can be better depending on the enemy's team comp. See below for further information. Approach Velocity: Approach Velocity actually has some fun synergy with Viktor's kit, as all slowed enemies grant Viktor bonus movement speed towards them, as long as they are slowed. With Viktor's W augment, this becomes a gateway that allows Viktor to have the movement speed to run anyone over. Time warp tonic: Time Warp Tonic, firstly applies half of the consumable's effect where applicable, then grants a 5% ms boost. Viktor would mainly gain advantage for this if he were to start Corrupting Potion.

An important skill in League of Legends is being able to adapt your build and knowing what items will optimize your champion in the job they need to do. Viktor is a high-damage mage where positioning can mean the entire game due to your damage output. You can build offensively, or defensively and still do the most damage in the game, as long as you position correctly. Keep in mind the opponent's main sources of damage so you can build proper resistances, and determine which utility you may need. The most obvious would be Zhonya's Hourglass and Morellonomicon if the opponents have champions such as Sylas, Dr. Mundo, or Zed, as Morellonomicon reduces healing, and Zed's Death Mark.

SUMMONER SPELLS

- FLASH: Very standard summoner. IGNITE: Ignite inflicts True Damage and healing cut (also known as grievous wounds). This is very strong into champions that you can all-in, champions that rely on healing abilities and champions who have stealth, as it additionally applies True Vision. I personally take this as the standard summoner spell. TELEPORT:Teleport allows more mapwide pressure, as you have the potential to gank any lane at any time. You can shove the wave and teleport back to lane with an item to gain an edge on your lane opponent. Be wary; teleport's initial cd is 6 minutes, and scales overtime. CLEANSE: Use cleanse into hard cc junglers and lane opponents. You can get rid of summoner spells targeted onto you, such as Ignite and Exhaust, as well as stuns, therefore allowing one to make offensive plays using cleanse if the opponent relies on hard cc. (Example: You can run into Veigar cage, get stunned, activate Cleanse and combo onto the Veigar. EXHAUST: Exhaust reduces incoming damage from one champion and slows that same champion. Use this into singular threats that have potential to oneshot you. Choose this into Zed, Talon, Yasuo,[rengar] or Yone if you need to ensure you don't die 1v1 in lane. While Exhaust is on CD, play safe, as you take this as a defensive summoner. BARRIER: Barrier can be taken into champions, such as Syndra and champions that are almost certain to take ignite in situations you would otherwise take heal, as it reduces your burstability. HEAL: Very HEAL summoner. Grants bonus ms and heals an ally for the same amount you heal. If you plan to skirmish in the jungle, this summoner can be very useful to clutch save your allies, especially when fighting for scuttle.

As Viktor, you can play very differently. If you prefer a poke-heavy lane then you can do that. If you prefer a scaling, safer lane, then you can also do that. Viktor is a flexible pick in terms of playstyle. While the lane can be majorly impacted by match-up, you can do a lot to pull the game into your favour through minion management and knowing Viktor as a champion.

As a general rule, shove the wave before you begin a roam. Look to build a wave that the opponent cannot miss without detrimental consequences then look to establish vision control in the river, which is the quickest pathing route. Viktor is a generally immobile mage, so roaming takes time without upgraded boots. Look to maintain mid priority during level 3-4 so you can be the first to arrive if the jungle breaks into a fight for the scuttle crab.

On first back at ~8-12 minutes, if you are able to buy Hex core mk-1, upgrade E Death Ray and you have the capacity to oneshot the casters with a single cast. Get used to this as you can nearly always collect all three casters per wave at any point of the game onward. Viktor thrives in the late game, so be sure to be able to farm until that point properly.

While this can happen, you should also be setting freezes at mid on Viktor. A freeze is where the enemy minions kill your minions faster so the wave doesn't move outside of where you want it to be. This will generally force the enemy to walk further than they should in lane, making the susceptible to jungle ganks.
Freezing: click here for a guide.

You can place your ultimate Chaos Storm onto the wave if you have low mana post-6 and recall to save time backing, while also being able to farm the current wave.

Viktor can use his W Gravity Field to induce a slow field. When your jungler pings to set up a gank for mid, start pathing to the opposite side of the lane so your lane opponent paths towards your jungler. They will want to stand opposite of your position in lane, and this brings them closer to your jungler. Additionally, by placing your slow field onto an area, your lane opponent will more than likely want to walk around it, rather than through it. You can use this to alter their pathing and overall delay them, allowing your jungler to come into lane and increasing the chance of a successful gank.

Use your Gravity Field to disengage enemies. If multiple enemies walk into your slow field and get stunned, place Chaos Storm and walk away, using Death Ray to chunk them even harder. You can pick anyone who's low off with Siphon Power and use the bonus ms for an even faster escape. Ideally, you want to be able to run through a choke point, place your gravity field, then walk away, but due to Viktor having the capacity to be a "hit and run" champion, you can turn a disengage to an abundance of kills.

AS the game processes, your job as an AoE mage becomes more prevalent as the game continues to spiral into what eventually is solo queue

Survive either beside, or with your team until you can use all your spells.

Understand what champions require priority in spells, and where to place your Gravity Field for either zoning or mass hard cc.

This section will focus on what situational items to use, and a full explanation of the "beginner build" preset I created.

Bramble Vest can be bought when the enemy will be able to target you with AD, regardless of how you position. Examples of these champions can include Yone, Yasuo, or Caitlyn. This buy nets you some armor, and grievous wounds when they auto you. Can be later fully bought into Thornmail.
Frozen Heart can be bought when the enemy is nearly all close-range (melee) champions. Frozen heart nets armour, mana, and cdr, as well as a unique passive that reduces enemy attack speed if they get too close to you. Defensive buy for survivability.
Iceborn Gauntlet can be bought for the same reasons as Frozen Heart, as it essentially provides a slow, a little damage, cdr, and armour. Defensive items are great items to rush against assassins, such as Talon, or Zed.
Nashor's Tooth can be bought if you desperately need the 20% cdr to cap 40%. Since it grants 50% attack speed, runes such as Electrocute, and Phase Rush can be triggered a little easier.
Zhonya's Hourglass is bought when there is a key ability that needs to be ignored, such as Zed's Death Mark or stalled such as Mordekaiser's Realm of Death. Never buy Quicksilver Sash unless into a champion with suppression, as it will never build into anything Viktor specifically needs. Only buy Quicksilver Sash of you believe you will be targeted every time by a suppression ability in team fights.
Seraph's Embrace can be bought in place of Luden's Tempest if you want a late game shield. Build into more mana-orientated items, such as Iceborn Gauntlet to achieve additional AP and survivability.
Rylai's Crystal Scepter can be bought if you need a stronger slow.
Randuin's Omen is a strong item against a crit-heavy comp. An example of this could be any comp with Yasuo, or Yone, as the adc is more than likely to build crit. Randuin's Omen heavily cuts incoming crit damage.
Hextech Gunblade and Hextech Rocketbelt both suffer some conditions when built onto Viktor. As a champion, you are very mana hungry, as your E Death Ray at max rank costs 110 mana. This means you should buy into some mana item other than Perfect Hex Core to sustain this. Because of this, the spikes that these hextech items generally have for other champions are delayed so much that it feels as though they aren't worth building, however they can still be very effective when placed into the right builds.
Spellbinder gives bonus ms and a large amount of AP.
Morellonomicon. Strange item to put into "situational", however there are better substitutes in pure stats that force this item to become situational. You gain health and AP with grievous wounds on top for buying this, and should only be bought into healing-orientated comps early (second or third item). Heal-orientated champions: Dr. Mundo, Sylas, Soraka

Learn the Champion Build Explained

The beginner build allows oneself to ease into the Viktor playstyle, as it gives the player health, mana, and a large amount of AP to work with. You learn Viktor's cooldowns without CDR, so you understand what abilities are easiest to spam and what abilities are required to be decisive.
Build in this order:
Doran's Ring + 2 Health Potion> Hex Core MK-1 > Catalyst of Aeons> Rod of Ages > Perfect Hex Core > Liandry's Torment > Rabadon's Deathcap > Void Staff
As AD mid laners are becoming strongest in the meta, see yasuo buffs, Rod of Ages's 500 health, mana, and AP values feel somewhat underrated.

Anyways,

you should always aim to rush at least Hex Core MK-1, and get the first upgrade. This helps as it boosts either stickiness with Siphon Power's augment, or waveclear and damage with Death Ray's augment. While you could immediately rush an item, such as Iceborn Gauntlet immediately for kite (even though Viktor's Gravity Field augment applies slow on Siphon Power and Death Ray), you're still missing out on the early mana and AP rushing the first hexcore provides.
IMO, rush your hexcore to at least MK-1. It's almost always worth it.

How does one win league of legends? The easiest answers would be Kill Pressure and Objective Control.

Viktor actually has some kill pressure post-6. If he can get a good Gravity Field that fully stuns an enemy target, his ultimate does unsuspected damage, as it's damage that ticks over 6.5 seconds. Knowing how much damage Chaos Storm does when fully exerted is the key to getting kills in lane post-6. Pre-6, lane phase should be generally calm, only trading or poking depending on rune choice.

After lane, against most players, as long as Viktor goes even, he can chunk enemies for at least half their health with one full chain of abilities.

Ability chains (combos):
Siphon Power > Death Ray > AA > Phase Rush/Electrocute trigger
Siphon Power > Chaos Storm > Death Ray > Phase Rush/Electrocute trigger
Gravity Field > Death Ray > Chaos Storm > Siphon Power> Phase Rush/Electrocute trigger

During team fights, Viktor will have one of the highest priorities on his back from the enemy team, as Viktor's burst AoE spells can single-handedly win a fight. Viktor has everything anyone could want in a midlane champion: bonus ms, hard cc, and high damage output.

As this is more based off the player, establish vision control around objectives your team wants. This can tell you when the enemy team initiates, for example, cloud drake so you can make potential plays around the map. Although not recommended, Viktor can splitpush due to his strong wave clear and self-peel, however due to your high damage, you don't particularly want to miss a team fight. You can get your team to run the 1:3:1 formation (1 top, 3 mid, 1 bot), with Viktor and two others in the mid lane, and push for towers more comfortably. If the enemy team contests the mid push, you can zone with W Gravity Field while the sidelanes continue to push. If the match with their own 1:3:1, force the fight into mid through poking with Death Ray and Siphon Power if they get too close.

Play around objective spawntimes and force your team to fight for them. A team fight is always what Viktor wants after a completed Perfect Hex Core, and if you can get an objective out of it, hey, free bonus. Make sure your team understands this and can communicate for when Dragon or Baron spawns.

Viktor is a fun champion to play IMO.

Some weaknesses that many find in Viktor is his low mobility, his high first-back cost (for Hex Core MK-1, and his low magic resist values. So these exist. To get around each of them, the answer would be farming safely. If you don't actively overextend and freeze the lane when possible, you won't die as often, which allows you to safely farm for Hex Core MK-1, buy boots faster, and correcting itemization choices to fit the game's needs.

So, that's all I have to say about Viktor. Hopefully, this has helped someway to better your own understanding of the champion, or help in someway for your own gameplay. Viktor is a fun champion IMO, so get in the rift and try some stuff out.

- ai darkfluid

oh, and if you could, comment about how to improve the guide, you know, if you feel like it. Thanks, good luck on the rift.

CHANGELOG

2020-08-10 - Added information to Itemization
2020-08-11 - Changed build formats
2020-08-17 - Updated runes for the inspiration tree, added threats/synergies, added build notes