Hello everyone ;) this is my first guide for a champion. I am a silver 3 illaoi main with currently 250k on her (i know i have no life). and i would like to give you my tips on how to play with her.

u take Deathfire Touch, i dont care grasp of the undying is good. this ability works perfect with ur e and is very good for illaoi.

PROS:

can sustain in a team fight from heals
tanky vs armor
a good carrier
mid game to late is really good
can 1v5 if not stuned
fun champ that has unique skills

CONS:

early game isnt the best
gets kited hard
weak when ccd
doesnt have cc
dies from ap champs really fast if u dont buy items

Laning with illaoi is really simple,if you are having a really difficult matchup u start q (champions like teemo quinn vayne and other ranged champs). But if ur vs someone like garen,nasus,tryndamere in the early game,u start w for farm and poke.
lvl 3 is when u should start trading,ALWAYS BE NEXT TO YOUR TENTACLES,doesnt matter where u are if u dont have a tentacle near u just run. But if u are next to a tentacle,a really good combo for dmg is e then q on BOTH the enemy and the spirit(if u can),then w. now if the enemy engages u when u try to combo like that instead of pressing w on the spirit u w the enemy,ur w does precent health dmg so its really good (DO THIS ONLY VS CHAMPS WHO DONT BLOCK UR W like a jax or teemo).
BE CAREFUL from people cancelling ur w (yes this happends alot).
lvl 6 is a really ez game, all u do is wait for them to engage u, e next to a tentacle then ult and get a free kill. (even vs a 1v2 or sometimes a 1v3 depends on how much cc do they have).

now if u had a really good game then u probably just finished the first turret in the game and it was really easy for u ;) now is when u want to gank other lanes ( get the herald for u if possible) and help your team to get stronger.
when u helped everylane and u all pushed atleast the first turrets u should all gather up mid and force a teamfight.
in a team fight u should flash ult in the enemy, because u will just get stuned and die faster than u think.
make them come to u,and let ur support or tanky jungler take all the cc for u.
REMEMBER:always stay next to tentacles the entire game.

you become a boss.
u can kill everyone in their team solo cuz of ur burst and heal.
ur very tanky.
u **** on people
just stay with ur team and dont throw the game :)