Phantasmal Fiend

A defensive 1/5 wall that hides a hard turn toward offense, and the design lives in the gap between its static body and what it can become with mana fed into it. The blue switch is the headline: pay one generic and one blue, and the 1/5 becomes a 5/1, a wall reborn as a clock at instant speed in a single activation. The black ability is the supporting tool, paying black mana to shave a point of toughness for a point of power, repeatable as many times as you can afford it. That repetition is its own lever: the creature can whittle its own toughness toward lethal on its own terms, giving it a strange resilience against effects that want it dead in a particular way. The off-color tax is the friction that prices all of this. Here is a mono-black creature whose best mode is gated behind blue mana, so the payoff costs you a second color you may not have, and the conversion into a threat asks how much mana you are willing to commit to a single blocker before it stops being one. It reflects an era when blue and black were experimenting with creatures that rewrote their own stat lines at instant speed rather than committing to fixed bodies, building combat math into the question of how deep a player would dig into their mana to flip a defender into an attacker.