Toxrill's Toxic Tide

A mono-black control-midrange deck that grinds opponents down with discard and efficient removal before slamming Sheoldred, the Apocalypse and Toxrill, the Corrosive as game-ending threats.

Toxrill, the Corrosive spreads slime counters on every creature each end step, shrinking opposing boards while its slugs multiply off dying creatures. Pair that with the heavy removal suite (Fatal Push, Bloodchief's Thirst, Cut Down) to keep the board clear and grow an army of 1/1 slugs. Sheoldred, the Apocalypse turns the opponent's card draw against them while fueling your life total, and combining it with Sign in Blood and Phyrexian Arena lets you draw aggressively while draining the opponent. Gifted Aetherborn provides early defense with deathtouch and lifelink, helping you survive to the late game. Rankle, Master of Pranks lets you trade dead cards for pressure and disruption simultaneously.

Keep hands with two to three lands, at least one discard spell (Thoughtseize or Duress), and either a removal spell or a cheap threat. Mulligan any hand without a way to interact before turn three, or hands that are all expensive finishers with no early plays. A one-land hand with no card selection should be sent back.

Early game: strip the opponent's key cards with Thoughtseize and Duress, then keep the board clear with Fatal Push, Bloodchief's Thirst, and Cut Down while setting up card draw with Sign in Blood or Phyrexian Arena. Mid game: deploy Sheoldred, Gifted Aetherborn, or Tenacious Underdog to apply pressure and stabilize your life total. Late game: resolve Toxrill, the Corrosive or Invoke Despair to take over the board, let slime counters and slug tokens overwhelm the opponent, and close out with Sheoldred draining them every draw step.

Fast aggro decks that go wide before your removal comes online can overwhelm you, and counter-heavy control decks can answer your expensive finishers before they land. Graveyard-based combo decks may outpace your interaction, and Toxrill's seven-mana cost means you need to survive to the late game to use it effectively.