Erratic Apparition

Eerie folds two distinct enchantment events (an enchantment you control entering, and a Room finishing its second unlock) into one trigger, and this Spirit is the payoff built to bank both: every qualifying enter and every fully unlocked Room fires one temporary +1/+1. The discipline is that the pump expires at end of turn, so between turns the body reverts to a 1/3 flier and only swells on turns where those triggers are actively stacking. That expiry is the interesting part, because the boost counts events as they happen rather than reading a permanent counter or scaling statically off how many enchantments already sit on the board. Its combat size on any given turn tracks how many enchantment events you can chain before you swing: since fully unlocking a Room and casting most enchantments happen at sorcery speed, the sequencing lives in your main phase, and the size the attacker shows up as is largely locked in by the time combat starts. Vigilance is what keeps the math from being a one-way street; the swollen body stays back to block after attacking, so a turn that lands three or four triggers gives you an evasive threat that also defends at its inflated size until cleanup. On its own it is a durable evasive blocker with no ceiling; how fast it clocks depends on how enchantment-dense the shell around it runs. It supplies the evasion and the trigger; the deck has to supply the events.