The Mycotyrant's power and toughness are each equal to the number of creatures you control that are Fungi and/or Saprolings.
At the beginning of your end step, create X 1/1 black Fungus creature tokens with "This token can't block," where X is the number of times you descended this turn. (You descend each time a permanent card is put into your graveyard from anywhere.)
Flood the board with Fungus and Saproling tokens while feeding your graveyard to trigger descend, then convert that wide army into damage—either through The Mycotyrant's trampling body or with overrun effects and aristocrat drains. You self-mill, sacrifice, and cycle permanents into the graveyard each turn to maximize the end-step token payout, snowballing into a lethal swarm.
Self-contained engine: the commander makes tokens every turn just for filling your own graveyard, which BG does effortlessly with self-mill and sacrifice.
Token-wide boards pair perfectly with anthems, overrun effects, and aristocrat drains for redundant win conditions.
Recursive and grindy—black/green excels at value, recursion, and out-attriting opponents.
Cheap three-mana commander whose stats scale automatically, so it threatens commander damage without much investment.
Heavily reliant on the commander being on the field; without it the deck is just a pile of tokens with no engine.
Vulnerable to board wipes that erase the token army you spent turns building.
Descend triggers only at end step, so the payoff is slow and reactive rather than explosive.
Limited interaction and no evasion outside trample—stalls against fliers and go-tall decks.
Generates a Saproling every upkeep and becomes a city's blessing anthem to overwhelm the table.
Add efficient sacrifice outlets and self-mill (Altar of Dementia, Viscera Seer, Stitcher's Supplier, Golgari Grave-Troll) to maximize descend counts every turn, then layer multiple aristocrat payoffs for redundant drains. Tighten the mana with fast rocks and dual lands, and include protection like Heroic Intervention and Boros Charm-style indestructibility to survive wraths. For higher power, lean into a combo finish—Mycoloth plus a sacrifice outlet and Pitiless Plunderer can loop into explosive boards.