Ghostblade Eidolon

Double strike is the keyword that punishes a creature for not blocking and rewards a creature for not being blocked, and bestow is the mechanic built to hang that kind of payoff on a body you already control. The marriage is the whole design: a 1/1 that wants to be ignored on its own, and a six-mana enchantment that turns whatever it lands on into a double-striking threat one point bigger. The bestow clause is what keeps the package from being a dead draw late: cast the Aura side onto an existing attacker and you get the payoff immediately, but if that creature dies, the Eidolon detaches and stands back up as its own body, a survivor instead of a casualty. That detachment is the structural answer to the old problem with combat-enchanting Auras, the two-for-one blowout when removal hits the host. The cost asymmetry is honest about what each mode is worth: three mana for a fragile body that needs help connecting, six for the version that makes another creature finish the game. Doubling first-strike and regular damage on a creature that was already getting through is the kind of effect that closes games in a single swing, which is exactly why the bestow price sits where it does.