Coldsteel Heart

Double strike Eternalize 3WW (3WW, Exile this card from your graveyard: Create a token that's a copy of it, except it's a 4/4 black Zombie Cat with no mana cost. Eternalize only as a sorcery.)

Exile target creature and all other creatures its controller controls with the same name as that creature. That player investigates for each nontoken creature exiled this way.

When this creature enters, investigate. (Create a Clue token. It's an artifact with "2, Sacrifice this token: Draw a card.")

Return all artifact, enchantment, and planeswalker cards from your graveyard to the battlefield.

Whenever another snow permanent you control enters, you may have target player mill two cards.

Exile the top six cards of your library. You may cast up to two sorcery spells with mana value 3 or less from among them without paying their mana costs. Put the exiled cards not cast this way on the bottom of your library in a random order.

Whenever Marit Lage's Slumber or another snow permanent you control enters, scry 1. At the beginning of your upkeep, if you control ten or more snow permanents, sacrifice Marit Lage's Slumber. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

Draw a card. Flashback 2U (You may cast this card from your graveyard for its flashback cost. Then exile it.)