As a mutating creature spell resolves, instead of entering the battlefield, it merges with its target into one creature. Its controller chooses to put the resolving mutating creature spell on top of its target or underneath it. You'll end up with a pile of cards (or tokens—we'll get to that in a second) that all represents a single creature.
Quote from SaltMaster 5000 »
There is a cycle of lands I'd like to recommend to you guys, the storage lands from Time Spiral. Saltcrusted Steppe
These are pretty powerful and often work playing off color. They're pretty cool.