Cryptoplasm

Most clones make their decision once, at the moment they enter, and then they live and die as whatever they chose. This one renegotiates the contract every upkeep. The body that enters is just a placeholder; the real card is the recurring decision to remain what it is or to become whatever has since shown up across the table, and crucially the copy ability rides along into each new form. That self-perpetuating clause keeps it from ever being a one-shot mimic: it never spends its identity, only rents it, so a defensive blocker this turn can graduate into the best thing your opponent untaps with next turn, then again the turn after. The cost of that flexibility is that it is always a turn behind: the upkeep timing means it cannot answer something at instant speed, and it copies based on what exists when your turn begins, not when you need it. It also commits to the new printed values wholesale, so copying something with a death trigger or a downside copies the downside too. The closest relatives are the upkeep-driven creatures that re-evaluate the board each turn rather than the enter-the-battlefield clones that lock in immediately, and within that small family this is the one whose entire job is patience: built for the player willing to leave a 2/2 doing nothing for several turns on the bet that the board will eventually hand it something worth becoming.