Cast the instant or sorcery that deals damage or causes lifeloss by paying its mana cost.
Holding priority, cast Worldfire by paying {5}{R}{R}{R}, exiling all permanents, all cards in all hands and graveyards, and setting each player's life total to 1.
Resolve the instant or sorcery cast in step 1, causing each opponent to lose at least 1 life or be dealt at least 1 damage.
Each opponent loses the game due to having 0 or less life.

Each opponent loses the game

Exile all cards in hands and graveyards

Exile all permanents

Near-infinite lifeloss for all players

Mass Land Denial

Instant or Sorcery that deals damage or causes lifeloss to each opponent

Worldfire

Wizards of Thay

Cast an instant or sorcery spell by paying its mana cost, triggering Ashling.
Holding priority, cast Worldfire by paying {5}{R}{R}{R}.
Ashling triggers, causing you to rummage.
Resolve Worldfire, exiling all permanents, all cards in all hands and graveyards, and setting each player's life total to 1.
Resolve the Ashling trigger from step 1, dealling 2 damage to each opponent.
Each opponent loses the game as a state-based action due to having less than 0 life.

Ashling, Flame Dancer

Activate Myojin of Roaring Blades by removing an indestructible counter from it.
Holding priority, cast Sway of the Stars by paying {7}{U}{U}, causing each player to shuffle their hand, graveyard and all permanents they own into their library, then causing each player to draw seven cards and set their life total to 7.
Resolve the Myojin of Roaring Blades ability, dealing 7 damage to each of up to three opponents.
Each opponent loses the game due to having 0 life.

Shuffle all hands, graveyards and permanents on the battlefield into their owner's library

Sway of the Stars

Myojin of Roaring Blades

Activate an animated land by tapping it, adding at least {U}.
Cast View from Above by paying {U}, targeting the animated land.
Orvar triggers, creating a token copy of the animated land that is not a creature.
Resolve View from Above, returning it to your hand.
Activate the land token by tapping it, adding at least {U}.
Repeat from step 2.

Infinite magecraft triggers

Infinite landfall triggers

Infinite storm count

Infinite tapped Island tokens

Card That Animates a Land

Orvar, the All-Form

View from Above

Cast Nameless Inversion from your graveyard, as it is a Knight card, by paying {0} due to Wizards of Thay and Morophon, giving a creature +3/-3 until end of turn.
If the creature has toughness 0 or less, the creature dies as a state-based action.
Repeat as desired.

Reduce the toughness of creatures opponents control to 0

Reduce the toughness of each creature opponents control to 0 upon entering

Haakon, Stromgald Scourge

Morophon, the Boundless

Nameless Inversion

On the end step prior to your turn, cast a copy of Channel from exile by paying {G}{G}, unpreparing Yavimaya Bloomsage.
Use Channel's ability by paying 1 life, adding {C}.
Repeat step 2 until you have exactly 1 life.
At the beginning of your upkeep, Near-Death Experience triggers, causing you to win the game.

Win the game

Near-Death Experience

Yavimaya Bloomsage // Channel

Combos with "Wizards of Thay"