Sac Payment??

[jimbo_karate]

If I have an evolving wilds on the field and play a Crosis's Catacombs and choose my evolving wilds, can I sac my evolving wilds in response without sacrificing my Crosis's Catacombs?

[CleanBelwas]

Unfortunately not.

It works like this.

Play catacombs. ETB trigger goes on the stack.

At this point you can either maintain priority and sacrifice evolving wilds, or resolve the ETB and bounce a land.

If you chose to sac, the evolving wilds thing happens first and when it comes time to resolve the catacombs ability, evolving wilds is no longer there to bounce.

If you chose not to sac, then you have to bounce it (or something else depending on board state).

Essentially, you can't take any additional actions while a spell or ability is resolving, you can only do things in response, which create their own abilities that resolve first. When you choose to resolve the catacombs ability, that has to happen before you can do anything else, like activating evolving wilds.