Niv-Mizzets diary

You can’t take extra turns At the beginning of your upkeep, you may cast an imprinted spell without paying its mana cost. Then if there are 5 or more cards imprinted of the artifact, sacrifice it and create a token that’s a copy of Niv-Mizzet, Firemind Imprint — Whenever a player casts an instant or sorcery spell, exile it as it resolves