Brokkos, Apex of Forever

Mutate is a stacking mechanic: one creature's abilities pile under another's face, and the whole arrangement lives and dies as a single permanent. That single-permanent fragility is usually the catch, because when the top card is a heavy investment, one sweep or a well-aimed answer collapses everything you built. This one attacks the problem from the other side. The graveyard clause means death is only a delay: as long as the card reaches the yard rather than being exiled, its mutate cost doubles as a recasting cost, so it can crawl back and drop onto whatever survived the last board wipe. It does not return the other cards that were mutated under it, so this is not a self-rebuilding pile; it is a body that keeps returning to become the new top of a fresh one. The Sultai identity is the rest of the reasoning. Bant and Jeskai want to protect what they commit; a black-green-blue wedge is happy to bin a creature on purpose and buy it back, treating the graveyard as a second hand. The hybrid pip in the mutate cost matters too, since it keeps the recursion from ever demanding all three colors at once. Trample is what converts the loop into a clock: a 6/6 that keeps coming back is a nuisance, but one that pushes damage past chump blockers is how the returns actually close the game.