As someone playing Illaoi for the majority of my games, I would say she isn't mastered as easy as everybody seems too think. It's very easy to screw up your game if you do it wrong. Also, her most common build paths are just wrong in my opinion. I tried the Black Cleaver build a few times, but it leaves her way too squishy.
Her core build path should be: Jaurims Fist, iceborn gauntlet or spirit visage depending on matchup, merc treads, finishing steraks, then the iceborn or spirit (depending what was build earlier). From there, it depends on what to build. If ahead and you want damage, build death's dance. This item is soooo good on her. As illaoi, you want to be as long as possible in the middle of the enemy team, with Black Cleaver this isn't possible, with death's dance it is possible. The rest of the items depends on what the enemy team comp is. I find build banshee's against ap comps, dead man's against ad comp and zz'rot or guardian angel against balanced comps.
All in all, I find her way more usefull as a tank, as she already has high base dmg on her own, then build her more ad en squishy, cause the enemy will just melt her down with a squishy build.
She has also one important thing: NEVER use your ult if you havent pulled a spirit. If you do this, you will be dead, cause the extra tentacle from the spirit is the extra dmg you need.
