Mordekaiser's Q--Mace of Spades--doesn't always apply on-hit effects.
When using Mordekaiser's Mace of Spades it doesn't always apply on-hit effects; this is especially noticeable when using Titanic Hydra. It seems to apply the first Q's Titanic Hydra proc, not the second and sometimes the third proc. It seems very inconsistent and I doubt this is intentional.