Human Torch

Cast any noncreature spell during your turn and the 3/2 body wakes up before combat with flying, double strike, and haste bolted on for the swing: a prowess-adjacent trigger that turns a creature which would otherwise trade into anything into an evasive threat hitting for six on an unblocked connection. The design leans on double-duty spellcraft: each noncreature card advances your plan and arms your attacker in the same turn, so the build wants a dense stack of cheap spells and rewards you with a hasty double-striking flier the turn he lands, provided you have something else to cast beside him.

The attack trigger is where the design tips into multiplayer. Pay a four-color sum on the swing and every point of combat damage he deals to one opponent gets mirrored onto each other opponent, converting a single hit into a table-wide burn. The tension between the two abilities is deliberate: the first wants your mana spent on cheap spells to trip it, the second wants a Jeskai-plus-green base held open on top of the attack, and threading both in one turn is the ceiling. Without that pull the design would fire on autopilot, so it forces you to pick your window. His fragility does the rest of the balancing: nothing in either trigger protects the body, so the plan lives or dies on landing an unblocked, spell-fueled swing at a table that can see it coming.