Ertai's Familiar

Phasing was Weatherlight's strangest keyword, a mechanic that treated a permanent as briefly not existing rather than removing it, and most cards that carried it used it as a defensive blink: dodge a Wrath, dodge a targeted removal spell, reappear next turn intact. This one inverts the logic. Instead of phasing being the safety valve, every phase-out becomes a cost paid into your own graveyard, three cards at a time, and the same trigger fires when the creature dies. The result is a body whose phasing actively grinds you down unless you stop it, which is what the activated ability is for: pay blue and the creature stays put through your untap step, locking it on the battlefield rather than off it. The design lives on that fork. Leave it phasing and treat the self-mill as fuel for a graveyard plan, or spend mana each turn to keep it grounded and let it sit as a stubborn two-mana attacker that simply refuses to leave. Phasing has always been hard to build around because it operates automatically, on a clock you do not fully control; bolting a mill trigger onto that involuntary clock turns a defensive trick into a recurring engine, and the counter-ability is the rare lever that lets you opt out of your own keyword. Most phasing cards ask you to lean on the mechanic; this one asks you to fight it.