Endbringer

Most untap-on-every-untap-step creatures gate the trick behind a single payoff: Seedborn Muse hands you a mana ritual, but the value is downstream of what you build around it. This Eldrazi folds the engine into one body. It untaps during each opponent's untap step, then spends those windows itself: a Tim ping at no cost, a colorless-fueled lockdown that taxes an attacker or blocker out of combat, or a colorless-fueled card draw. The colorless requirement is the constraint that prices the better modes, since the cheapest activation (the one damage) is the only one that runs on the tap alone. What that buys is a creature taking up to four turns of activations per turn cycle in a four-player game, throttling whatever it can reach: pick off a mana dork on one player's turn, freeze a swinging threat on the next, refill your hand on the third, and still hold up the ping on your own. Damage that small reads as harmless until it is the only thing standing between an X/1 utility creature and its owner. The 5/5 body is incidental to the package; nobody runs this to attack. It is a control valve that happens to have legs, the rare repeatable interaction that scales with the number of opponents rather than diluting against them.