theft cards mtg MTGNexus Mint / near mint condition trading card MTGNexus - Fore-Theft

It also has access to bounce spells like Into The Flood Maw, which can bounce an Agatha's Soul Cauldron after it exiles Vivi to permanently get rid of that Vivi copy

Peer Past the Veil Peer Past the Veil is kind of a wheel effect, especially if you overperform on your delirium

From a story-crafting/game-design vantage point, Hunted Witness is a thing of beauty

Merfolk SovereignMerfolk Sovereign Merfolk as a creature type has no shortage of lords

I can see an argument for having it be S-Tier (the ability to sacrifice a creature for free to draw a card is super powerful, potentially enough for it to show up in multiple decks) or even B-Tier (while various Sacrifice decks seem like the most obvious home, it's possible that the lists are so tight that it will be hard to find room for Yawgmoth, Thran Physician)