Legacy Mono-Black Depths by Delthar
Your plan to get Marit Lage into play is also enabled by four copies of Expedition Map to make the whole thing more consistent, as well as giving you the chain of Urza’s Sagas to outgrind the Jeskai Control decks and Uro piles that are still popular in Legacy.
You’re not a Turbo Depths deck with Mox Diamond and Elvish Spirit Guide, even there’s four Dark Ritual. They’re only there to power out the turn one two-drops (Dark Confidant or Dauthi Voidwalker) and a discard spell (Thoughtseize or Duress), which will let you gain card advantage while handling the opponent.
The sideboard is also quite unique with four copies of Helm of Obedience. You can combo kill the opponent in combination with Leyline of the Void or Dauthi Voidwalker like they used to do in the past with UW Miracles with Rest in Peace.