Phantasmal Mount

A flavor mechanic literalized into rules text: this is a horse made of illusion, so mounting it binds two creatures' fates together. The tap ability hands a small creature a temporary buff and flight, but the two leaves-the-battlefield triggers form a mutual-destruction clause: if either the Mount or its rider dies before end of turn, the other gets sacrificed too. That symmetry is the whole design. Most Illusions of this era carried a self-destruct drawback as the price of their stats (Phantasmal Terrain, the later Phantasmal Bear and Phantasmal Image all wear "illusory" as a sacrifice condition), but here the fragility is contagious: the buff you grant is borrowed against the survival of the granting creature. The toughness-2-or-less restriction keeps the target pool to the weenies an Illusion deck was already fielding, which means the bonus most often lands on something nearly as fragile as the Mount itself, doubling the exposure rather than insulating it. It reads as a combat trick that wants to push a flyer through for lethal, but the linked sacrifices make it a high-variance gambit rather than a safe pump: one removal spell or chump block once the buff has resolved can take both creatures off the table at once. A clever piece of early-game design that asked players to weigh a temporary evasive edge against the chance of a two-for-one disaster, all dressed in the conceit of an unreal steed that vanishes the moment its rider does.