Faceless Devourer

Shadow built itself a closed combat lane: these creatures only interact with each other, so a board of shadow facing a board without it amounts to two armies passing through the same air. Inside that walled-off subgame, this is the removal piece. Its enters-the-battlefield clause exiles a rival shadow creature, and because shadow decks lived or died on having a body the opponent could not block, removing one is removing the whole exchange, not just a blocker. The catch is in the leaves-the-battlefield clause: the exile is conditional, not permanent. Kill the Devourer, bounce it, sacrifice it, and the stranded creature comes straight back under its owner's control. That makes it a temporary answer wearing the costume of a hard one, and it rewards pressing the advantage at once rather than sitting on it, because the clock to give the creature back is your own continued presence on the board. It reads as a flicker target waiting to happen, too: any way to blink it re-fires the exile and resets the hostage, though within the narrow shadow ecosystem there were rarely enough levers to abuse it cleanly. The card belongs to an era that loved building parallel rules-spaces: a mechanic so isolating it needed its own removal, its own evasion, its own arms race, all conducted between creatures nobody else on the board could touch.