Teferi's Veil
Phasing as a mechanic was Mirage block's attempt to model "here but not here," and this is the card that flips the keyword from a defensive dodge into an offensive engine. Every creature that swings phases out at end of combat, which means it untaps the long way around: it ceases to exist until your next untap step, then phases back in. The strategic payoff is in what disappears with it. During your opponent's turn the attacker is simply gone, untouchable by removal, immune to a sweeper, impossible to tap down or steal, and it returns ready to attack again because phasing in is not entering the battlefield. The price is steep and self-inflicted: a creature that is phased out cannot block, so every swing leaves you defenseless until it returns. That is the real tension, an aggressive board that can never sit back. Note the quirk of the original rules: enchantments and counters phase out alongside the permanent they are attached to, so an equipped or pumped attacker carries its baggage cleanly through the loop. The design comes from the moment Wizards was probing how far phasing could stretch as a constructed concept; the keyword mostly retreated to flavor and reprints afterward, but the idea encoded here (an attacker that is invulnerable during the opponent's turn) is one the design team has revisited in narrower, more controllable forms ever since.
