Spirespine

A 4/1 that must block whenever it can is a body built around a single tension: stats that big on the front and that fragile on the back only make sense once you accept the creature is rarely choosing its own fights. Cast as a creature, it is a wall that trades up against most attackers before dying, though nothing stops it from swinging in: a tapped creature is not able to block, so attacking is the legal way out of an inconvenient forced block. The bestow line inverts the usual aura math. Most green pump exists to turn a body into a swinging threat; this buys +4/+1 and pays for it by conscripting the host into defense every combat. The natural home is your own blocker, where the forced-block clause is free because the creature meant to hold the ground anyway, and the buff turns a chump into a brick that eats attackers all game. Bestow also smooths the classic aura blowout: kill the enchanted creature and the Spirespine does not follow it to the graveyard; it reverts to being a 4/1 and lives on. That second life comes with a catch, though, since bestow is an alternate casting cost rather than an equip ability: once it has fallen off and gone back to a creature, it cannot reattach itself. A narrow piece, but an honest one, where an oversized buff is made fair by binding the recipient to defense.