Traitor's Clutch

Shadow is the rare evasion keyword that walls off combat from both directions: a creature that has it can engage in damage only with other shadow creatures, which in practice means nothing on the board can stop it. Hand that out as an instant and any attacker becomes an all-but-guaranteed connection, with the +1/+0 there to tip a race or shove an equipment trigger through. What separates this from a disposable combat enabler is the second cast: the same evasion returns from the graveyard for a sliver of the full price, so one creature can land two unblocked hits across a game, or two creatures can each take a turn slipping through. That repeatability is the whole pitch, because the five-mana front end is a steep ask for a temporary buff, while the cheap, instant-speed, self-exiling flashback half lets the card operate as a two-stage finisher: push damage now, then drain the rest from the yard later. It sits among the grants that make a creature unblockable by changing what it is rather than what it has, and the shadow version is the most total of those: it does not fly over a defender or outsize one, it removes the creature from the reach of all but other shadow creatures.