Sion Tiamat Bug

When Sion enters his passive while having an item that builds out of or is Tiamat then it will not use the passive AoE damage on hit unless you activate the item, then it allows you to use the effect.

(Simplified) - When Sion enters zombie mode the tiamat item does not work until you use its active effect

(Bonus) Sion ult doesn't proc sudden impact on the leap part of his ultamite, this could be easily resolved by adding two requirement flags to his ult that if met will give him the rune effect, just make it so if his ult does not reach the end of its channel then the buff is not given, as the only other two ways to proc it are by recasting or reaching the end of the channel (both of which result in a leap)