Layers is something I've always needed help with, and I know that Mutate interacts strangely with other layers since it, like, modifies the base layer or something? If an opponent has enchanted my creature with Reprobation and I mutate Cavern Whisperer onto it, what happens?
Mutate isn't really as complicated as most people think it is. A mutated creature is basically just the top card of the mutate stack with all of the abilities of the other cards in the stack. Just add their text boxes on to the top card's text box and that's what the creature is.
The abilities of all the cards that make up a mutated creature are consdered to be its printed abilities, so a card like Reprobation will remove all of them, no matter when they were added to the mutated creature. (A mutated creature's timestamp is the same as that of the earliest card in it. Every other card merged with that permanent and so no new timestamp was created.)
For example, if a mutated creature has Reprobation on it and you mutate a Gemrazer onto it, you won't get Gemrazer's mutate trigger or any other mutate triggers for it since Reprobation removes all of the printed abilities.
