Possible Sion turret glitch?
I was messing around in an AI game with a friend as Sion when I died next to a turret and went into my undead mode. We ran out of minions and I was going to tank it, but the turret IGNORED me and went for her even though she was much farther away! On a somewhat related note, in one of the following games no matter how much I killed I didn't gain any bonus HP from W.