Mercurial Geists

A 1/3 flier that idles as a serviceable blocker until spells begin flowing, then flips into a clock: every instant or sorcery you cast pumps it +3/+0 for the turn, so two or three cheap spells in a window turn a wall into a 7/3 or 10/3 evasive finisher out of nowhere. Toughness stays pinned at 3 no matter how many triggers stack, which is the balancing wrinkle here: the creature never gets harder to kill, only faster, so it rewards a shell already chaining spells rather than one trying to shield a fragile threat. It belongs to the spells-matter lineage that periodically pairs a modest evasive body with a cast trigger; Kiln Fiend and Nivix Cyclops are the red-side cousins, swinging on power for the turn, but the blue half buys flying outright instead of a ground-pounding alpha strike. Where those one-toughness cousins fold to any incidental burn or a stray blocker, 3 toughness lets this one survive a scattering of small damage and still connect the turn it goes off. The trigger counts the act of casting, not the payoff, so cantrips and counterspells feed the swing exactly as well as anything with a board impact; a deck content to durdle on the stack still gets a real threat out of the same cards it was already holding.