Hello! Welcome to my first guide on Mobafire. :)
I have tried Lux several times when it was free to play and fell in love with her. Ever since I bought her at Level 10, She was my main champion. People say that Lux is weak and doesn't belong in any lane or even the entire game, but I feel that she is very strong and also has awesome CC. This guide is for an AP carry mid laning Lux. Read on and follow this guide to success in playing Lux! :D

Note: Do not expect a 100% success after reading this. This cheat sheet is how I play Lux, don't follow it exactly as I am not the greatest Lux player.

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Pros +A lot of CC +Epic range +Vision Skill +Easy to play and master +Great Shield

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Finales Funkeln

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Cons -Very Squishy -Mana Hungry -Low Burst Potential -High CD on all of her spells -No escape tactics

The 9 Greater Glyph of Scaling Ability Power are crucial in an AP carry Lux for both early and late game as, obviously, it increases your AP and your damage done by abilities.
The Greater Quintessence of Ability Power is a classic AP carry rune. It's seriously self explanatory. 15 AP at level one? Why not? And if you use the level scaling one, the difference is only 9 AP.
Because of early mana problems, I chose the 9 Greater Seal of Scaling Mana Regeneration to increase Mana Regen and enable a longer stay at mid lane during the laning phase, and even go and help your allies when you successfully harass or kill an enemy.
Lastly, you would always want more damage so I picked the 9 Greater Mark of Magic Penetration to have some magic penetration. Since you will be using a lot of magic (obviously), this will help a lot.

Your Passive skill is Illumination, which marks and opponent after getting hit by a damaging spell. The mark can be set off by auto-attacking the enemy unit and will set it off, making your auto-attack deal additional 10+(10xLevel) damage. This skill is especially good for harassment but you will have to go closer to your target to set this off, risking your life a little.
Your Q is Light Binding. It hits the first two enemy units in it's path and snares them while dealing damage. However, the second victim will only receive half of the effects, which means half damage and half snare time. IMO, this skill is basically the Light version of Morgana's Dark Binding, just that it hits two enemy units.
Your W is Prismatic Barrier. Lux throws her wand like a boomerang and produces a shield on any ally in its path. At the end of its range, it comes back to Lux and refreshing the shield on allies it touches. This shield is especially useful in team fights if you can successfully protect your whole team.

Note: Prismatic Barrier is sure to hit Lux twice. You can alter its course by moving around before it comes back as it will definitely go to you. So if you miss the first, try to make use of this to let it hit your allies.
Your E, which is extremely useful, is Lucent Singularity. Lux fires and orb which deals AoE slow and detonates after 6 seconds, damaging anyone in the range. You can detonate it early by pressing E again. This skill has another function, which is to prevent ganks. You can plant it in the brushes or anywhere that you cannot see for vision, which is extremely useful considering your squishiness and that one well done gank can easily kill you. It is a great utility spell.

Note: This skill also provides vision for your enemies, so don't go randomly placing them in where you are waiting to ambush and trying to "protect" yourself if anyone comes too close.
Your ulti, the pride and joy of Lux, is Final Spark, or if you prefer the old name which Mobafire still uses, Finales Funkeln. With its amazing range of 3000, it can help both you and your team. It can take down low health escaping foes, help other lanes do that, provide short periods of vision (not recommended), and KS (not recommended too). With a short cooldown and pretty decent damage, this skill comes with a small sacrifice to nerf it: a 0.5s channeling time.

Firstly, you pump your Light Binding for the higher damage and lower mana cost. And also since you are in the mid lane, you wouldn't need much AoE. At the next level, you pump your Lucent Singularity. By now, you should be able to gain your first blood. Then you have a point in Prismatic Barrier for the defense. Now prioritize your skills in the following order: Finales Funkeln > Lucent Singularity > Light Binding > Prismatic Barrier

This is because Lucent Singularity is used more often and there is a better improvement in damage and a lower cooldown. Light Binding is also good but pumping it does not improve on the snare duration, so I do not recommend it. And of course, you pump your awesome ulti whenever you can.

The basic level 2 combo:
Light Binding > Lucent Singularity(don't detonate) > auto attack > detonate Lucent Singularity > auto attack
At level 2, this should probably send your enemy recalling back.

At level 6 and above;
Light Binding > Lucent Singularity(don't detonate) > auto attack > detonate
Lucent Singularity > Finales Funkeln > auto attack
You might want to do a level 2 combo before this to weaken and also kill the enemy.
Also, bear in mind that Finales Funkeln detonates your Illumination debuff.

Ignite is a good DoT summoner spell which inflicts grievous wounds, halving the healing capabilities of the one target. This is a good skill to start your burst with as it prevents the enemy from healing much after you damage them. In teamfights, try to target the AP or AD carry to kill them more easily and prevent your team from being mortally wounded. Plus, with Summoner's Wrath , you get extra 5 AP and AD when this spell is on CD.
Flash is a must have for every single champion. With multiple uses like gap closing and escaping, even flashing after someone who had just flashed away. You can flash through walls, and also places where you don't have vision in, unlike Katarina's Shunpo. Sadly though, you can't abuse it with that super long cooldown.
Heal is a great summoner spell that saves lives. A viable option if your opponent is a good harasser or of you wish to play support. If you pick this, you might want to use a point in Summoner's Resolve instead of either Summoner's Wrath or Summoner's Insight , whichever makes more sense.
Clarity is a good choice for those with Mana Problems and cannot control their usage of spells. Good for beginners to Lux as she is very Mana hungry, unlike some others.
Cleanse is good if your opponent spams CC like it is nothing to them. (e.g. Veigar, Cho'Gath, etc.). However, your long range makes you a less vulnerable champion and should most likely not be hit a lot.
Teleport is a good choice as it has many uses. For example, you can use it to gank, get back to lane fast, or a 4 second recall which cannot be interrupted(not recommended).
(Note: Can be used on minions)
Ghost is another great escape and chase. Use with flash for ultimate mobility.

The others are a no-no as they are quite useless.

We start off with a Boots and 3 Health Potions as this increases your survivability as you can dodge attacks more easily and to recover health quickly when you get hit.
Then, we get 2 Doran's Rings for more health for sustainability, more AP for damage, and Mana Regen for staying in lane.
Next, we upgrade our boots into the Sorcerer's Shoes for Magic Penetration. At this time, most people will have a flat 30 Magic Resistance and with times and this item, you get around 29 Magic Penetration.
Because Mana Regen is too important, we try to get our Athene's Unholy Grail early by making a Chalice of Harmony first. This item is just too OP in terms of Mana Regen, provides good CDR, great AP, and also Magic Resistance for the squishy Lux and reduce damage taken.
We then try to get the Rabadon's Deathcap for the insane AP boost. As one would for making it, get a Needlessly Large Rod first.
The next item we get is the Sheen, which has a unique passive which stacks and goes well with our passive, Illumination.
The Void Staff is good for damage as it provides a good amount of AP and Magic Penetration. This maximises our damage output against anyone. More damage dealt can't be a bad thing.
Our Sheen is then upgraded into a Lich Bane for the added AP, Magic Resistance, Mobement Speed, and Mana. All these benefit you and don't waste a slot, why not get it? The only reason why it was taken later is because the Passive is the same as the Sheen and a Void Staff Would increase damage more than upgrading your Sheen into a Lich Bane.
The last item which we get is the Zhonya's Hourglass. It gives great AP and Armor, plus that awesome Active which makes you an invincible statue for 2.5s. It's great defense which could save your life.

Mejai's Soulstealer is a great item -- the only one that can beat Rabadon's Deathcap in terms of AP, and also gives you much needed CDR. However, to do that, you will need stacks and once you have them, your enemy is going to target you and try to shut you down. So this item is a curse in its own way as well. USE AT OWN RISK
Archangel's Staff is an item that provides you a good amount of AP, which increases as you cast more spells, and also some Mana. It's a good it's a good item to use for AP, just that you do not have enough space for it. If you think you don't need defense, you can replace your Zhonya's Hourglass with this.
Rod of Ages is a good item early and mid game because of the mana and health Regen per level. However, it gets useless at level 18 as you don't gain the Regen anymore and there are other items that give more damage than it. So, you can have it at the start, but make sure to sell it once you get to level 18 and need space for other items.
For that good AP and Spell Vamp, nothing comes as cheaply and with high quality as the Will of the Ancients. You would want to have this for sustainability and damage. Banshee's Veil is great if you are having a hard time sustaining your opponents' spells. It provides good Magic Resistance and a spellshield which can save your life. Overall a good defensive item.

Deathfire Grasp used to be awesome, in fact, it could bring your opponent down half health before you start your burst, with only a one minute cooldown, essentially being a second ulti. Used to be great burst, but it got recently nerfed and is now almost useless, other than CDR and AP.
Abyssal Mask used to be a must have for all AP carries. But it was nerfed from a 1000 range to a 600 range. Since Lux is usually out of 600 range if you play her right, it's useless other than AP and Magic Resistance.

The Crest of the Ancient Golem (a.k.a Blue Buff) is obviously great for a Lux, as the CDR helps a bunch as well as the Mana Regeneration. All of which Lux seriously needs.
You can use your Lucent Singularity to spy on the Baron Nashor and also the Dragon. You can use Finales Funkeln to ks the opponent of these two kills or even the blue buff. At your own risk though, don't blame me if you get flamed, reported and targeted.

Credits to jhoijhoi for the template, which you can find here, and also for that BBcoding tutorial.

A big thank you to you for reading my guide. Vote and comment please.
And thanks if you helped me in one way or another.

If you want to give me suggestions or links to pictures, you can comment on this guide. Alternatively, you might want to email me at jonaschow9999@yahoo.com.sg
If you read this guide and used it to play and had a good score, please email a screenshot to me too.
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Thank you and have fun playing as Lux!

21/10/12: This guide was created
22/10/12: This guide was drastically improved on in terms of design, BBcoding, and content
26/10/12: The Deathfire Grasp has been placed into a new section, Items that were nerfed
27/10/12: Ionian Boots of Lucidity has been replaced with Sorcerer's Shoes
29/10/12: Formatting changed slightly. No Magic Resistance? chapter added. Will of the Ancients into the other viable items.