Hi, After the 6.5.0 update, I noticed that Omniscience doesn't change Niv Mizzet, Parun's casting cost to 0 anymore. The dragon has a protectiom against his mana cost being raised or his acquired mana being drained but it should not affect the ability of Omniscience to lower the mana cost to 0.
this happened to me today too
Same thing happened to me and at least two other people that I know of. All playing Omniscience and the same Niv Mixzet
Omniscience is doing this on a lot of cards, not just Niv
@RiverLethe said: Omniscience is doing this on a lot of cards, not just Niv
Basically anything that "can't have it's mana drained or raised", like Void Rend, also now doesn't seem to be able to have it's cost lowered.