Entropic Specter

Read an opponent's hand, then attack that same resource, and you have a closed feedback loop. Because the relevant player is locked in by a choice made as the creature enters, this is not a characteristic-defining ability: anywhere but the battlefield the Specter is a 0/0, and once it resolves its power and toughness track the chosen player's hand size and resize continuously as that hand grows and shrinks. The design tension falls out the moment you trace it. The creature is largest against a hoarding control opponent and smallest against an empty-handed aggressor, so it swings hardest precisely where its evasive body is least needed to race, and shrivels against the decks a five-mana flier would most want to pressure. The discard-on-damage clause then feeds back into the sizing: every hit on the chosen player thins that hand, and every such hit therefore shrinks the Specter. It is a self-limiting clock. The more it disrupts, the smaller it gets, until against an opponent who has dumped their hand it is a 0/0 that dies where it stands. That self-defeating curve is the friction holding back what would otherwise be a runaway disruption engine. As a Specter, it belongs to a long black lineage of evasive discard creatures tracing back to Hypnotic Specter; but where its forebears strip cards at a fixed rate regardless of board state, this one sizes itself to a single opponent's hand and then eats away at the very number keeping it alive.