Lovely example of Sion's ulti pathfinding

In case it's not obvious from the video I ultied towards blitz that was running away and somehow anivia's stunball redirected me.

This isn't the first time sion's ulti did some weird pinballing. Also why does it even consider Anivia's stun icicle as an unpassable terrain. Fix poor fella. He is already nearly useless compared to his other tank brethren.