mtg three sided card Shapeshifter (3/2) Commander Lost Caverns Ixalan Token NM x4 - Magic Token Creature — Shapeshifter Changeling (This token is every creature type.) Terra, Magical Adept - Esper

This is where the notion of computational complexity comes in

After sideboarding, you can change what the game is about, abandoning your low-impact creatures that would get caught in sweepers and instead presenting a midrange deck similar to theirs, but with counters and Eldrazi, and surprise them with a plan of going over the top of them without overcommitting to the battlefield

Shoot, you can even Reality Shift your own stuff, especially if you know what's on top of your library (via Soothsaying or some such)

Its never been reprinted (a travesty, if you ask me), so I cant show you the updated Oracle rules text on a card, but I can tell you what it would be if we ever saw Marble Priest again: All Walls able to block Marble Priest do so

Persist: Resurrect your best creature