Hello my name is NDarKnight and i hope this guide will help you to win games i play with this guide and its good guide try it out. The most awesome thing with illaoi is that she dont have counters you can see in threats that only urgot and teemo have more chance to beat illaoi than others. Anyway i hope you like the guide.

Most of Illaoi player take Ignite and Flash but i prefer using Teleport cause on late game you really need it to deff base etc. so using Teleport isnt that bad.You can go Ignite too but your teemates are going to complain cause you dont deff base on time so i would recommend using Teleport. You can take Teleport and Ignite that is not bad idea but you need to play carefully. Teleport is nerfed so most of you thinking about taking Ignite rather than Teleport but Teleport is still great just use it when you really need it.

For Illaoi items i dont have too much to talk about it you need to buy Black Cleaver cause its core item for almost every tank on top it will make you tanky and will give you damage so its great item its core item and for boots you can take Ninja Tabi if you play against ad and if you play against ap you need to take Mercury's Treads and Sterak's Gage is similiar to Black Cleaver its core item for illaoi and Spirit Visage is core item too you need to buy it for first item if you play against champs like teemo or vikor or any ap champ on top and taking Guardian Angel is brutal you will be tanky as hell you will do allot damage and if they kill you, you will revive and kill them all thats it.

Prophet of and elder god-passive
Illaoi and the Vessels she creates spawn Tentacles on nearby impassible terrain. Tentacles swing at Spirits, Vessels, and victims of Illaoi's Harsh Lesson, dealing physical damage to enemies hit. If you plan to use Leap of Faith just look do you have enouf of Prophet of an Elder God on your lane.
Tenctacle smash-Q
Range: 850
Cooldown: 10 / 9 / 8 / 7 / 6 Cost: 40 / 45 / 50 / 55 / 60
Passive: Increases all tentacle damage by 10 / 15 / 20 / 25 / 30%. Tentacles that hit enemy champions heal Illaoi for 5% of her missing Health.
Active: Illaoi summons a tentacle that slams down in a target direction, dealing 10 x level physical damage to all enemies in a line. I prefer using it after i catch enemy with Test of Spirit.
Harsh lesson-W
Cooldown: 4 Cost: 30
Illaoi leaps to her target, dealing her total attack damage plus 3 / 3.5 / 4 / 4.5 / 5% of the target's maximum health (+2% per 100 attack damage) bonus physical damage and causing nearby Tentacles to also swing at the target. Its great cause it doesnt let enemy with low hp flee.
Test of spirit-E
Range: 900
Cooldown: 20 / 18 / 16 / 14 / 12 Cost: 35 / 40 / 45 / 50 / 55
Illaoi hurls a tendril forward in a line that stops at the first enemy hit. If the enemy was a champion, the tendril pulls their Spirit from them and places it before her. The Spirit is connected to the target by a tether.
The Spirit has 100% of their current Health and lasts for 10 seconds (reduced by 1 second each time Illaoi receives damage from the target champion).
Over the duration, the Spirit can be attacked by Illaoi and her allies. 25 / 30 / 35 / 40 / 45% (+8% per 100 AD) of the damage dealt to the Spirit is also dealt to the target.
The tether will be severed if the Spirit is killed or when the target moves too far away, slowing the target enemy by 80% for 1.5 seconds and marking them as a Vessel, causing them to spawn a Tentacle every 5 / 4 / 3 seconds for the next 12 seconds. The spawn rate is increased every 6 levels.
Leap of faith-R
Range: 500
Cooldown: 120 / 105 / 90 Cost: 100
Illaoi leaps into the air before slamming her idol into the ground, dealing 150 / 250 / 350 (+0.5 per bonus attack damage) physical damage to all nearby enemies and summoning a Tentacle for every enemy champion hit. For the next 8 seconds, Tentacles swing 50% faster and are untargetable while Harsh Lesson has a 2 second cooldown.

Kleptomancy
After using an ability, your next two basic attack within 10 seconds against a champion grants 5 gold. Occasionally, you will gain a consumable item instead. If you gain a consumable item while your inventory is full, the consumable will instead be consumed. Kleptomancy cannot be activated more than once every 2 seconds.This is really great rune it can save you and can get you gold advantage you need and this is the my best rune for illaoi.
Magical footwear
PASSIVE: At 10 minutes (-30 seconds per Damage rating Takedown), you gain Slightly Magical Boots item Slightly Magical Boots for Gold free. Slightly Magical Boots are identical and can be upgraded as if Boots of Speed item Boots of Speed. If the inventory is full while receiving the boots, they will appear as soon as a place in the inventory is freed.
Additionally, your boots gain PASSIVE: 10 bonus Movement speed icon movement speed.
However, Boots of Speed item Boots of Speed are disabled and you cannot purchase tier-2 boots prior to obtaining Slightly Magical Boots.
Biscuit delivery
PASSIVE: Receive a Total Biscuit of Everlasting Will item Total Biscuit of Everlasting Will at 3:00, 6:00, 9:00 and 12:00. If the inventory is full while receiving a biscuit, the biscuit(s) will appear as soon as a place in the inventory is freed.
Consume a Biscuit to restore 15% of your missing health and 15% of your missing mana over 15 seconds, as well as permanently increasing your maximum mana by 40. You will also gain the increased mana if you Gold sell the biscuit for Gold 30.
Manaless resource Manaless Champions restore 20% missing health instead. Can hold up to 4 biscuits at the same time.
Additional biscuits can be obtained with Kleptomancy rune Kleptomancy, which grants increased maximum mana only in conjunction with this rune.
Time warp tonic
Consuming a potion or biscuit grants 50% of its health immediately, and mana if applicable, but prevents that consumable from being used again until the effect ends. Health/mana per tick is then reduced by half for the effect's regular duration.Really great combined with kleptomancy if you take kleptomancy you should take this too.

Sudden Impact
Going in combat by affecting an enemy champion within 3 seconds of using a dash, blink or Teleport Teleport, or exiting from Twilight Shroud old2 invisibility or Ambush 2 camouflage, grants 7 Lethality and 6 Magic Penetration for the next 5 seconds. If the triggering effect deals damage it will also benefit from the penetration. Cooldown is 4 seconds after using it, and this is really great for your dash you will do extra damage and it can maybe help you to make a kill.
Ravenous Hunter
Heal for 1.5% (+2.5% per Bounty Hunter stack) of the damage dealt by your abilities, on-hit effects and items, up to 14% at 5 stacks. Benefits from Heal power Heal Power. Earn a Bounty Hunter stack for champion Damage rating takedowns, up to one per unique enemy champion. This is great rune it will get you allot of damage and you can go tanky items without worrying about damage.

PROS:
+Tanky
+Consistently high damage
+Great Wave Clear
+Strong Mid game
+Great team-fighting
+Fun to play

CONS:
-Can be kited easily
-No hard cc
-Ulimate is outplayable
-Mana issues early-game
-bad against champion who can easy flee like gnar or shen etc.
-Ult long cooldown

I would like to talk how to beat illaoi, if you dont know how to beat illaoi you wont know how to deff. when you play illaoi Whenever possible, take out tentacles, so she can’t use them to hit you with Harsh Lesson.
Don’t kill her tentacles when you’re the Vessel. Instead, dodge the first attack from a tentacle and stand next to it so a new one can’t spawn and attack you again.
Test of Spirit-E spirits last for 10 secs, but their duration go down every time Illaoi is damaged. Fight her if you’re healthy enough, to stop her from dealing damage to you via the spirit.
Moving sideways whenever she moves forward or hiding behind minions is a good way to dodge
Test of Spirit-E.
Illaoi has no escapes and is generally easy to catch out, but she wants the fight to come to her. Without her Leap of Faith, she’s easier to kill as she won’t have as many healing sources.
Illaoi heals by hitting you with her tentacles, so she’s easier to fight in spaces where her tentacles have been taken out.
Lvl 6 is all Illaoi needs to start consistently winning duels and turning around ganks with Leap of Faith. Illaoi dont have counter's you just need to watch out on how you play.