Donate Demonic Pact to an opponent.
At the beginning of the opponent's upkeep, Demonic Pact triggers, causing them to select the fourth mode and lose the game.

Target opponent loses the game at the beginning of their next upkeep

Demonic Pact

Iroh, Tea Master

Donate Karlov Watchdog to an opponent.
During the opponent's turn, activate Altar of Dementia by sacrificing a face-down creature you control.
When the creature dies, Yarus's second ability triggers, returning it from your graveyard to the battlefield face-down as a 2/2 creature, and then not turning it face-up due to Karlov Watchdog.
Resolve the Altar of Dementia ability.
Repeat from step 2.

Infinite creature LTB

Infinite creature ETB

Infinite creature sacrifice triggers

Infinite death triggers

Infinite mill

Infinite self-mill

Yarus, Roar of the Old Gods

Karlov Watchdog

Altar of Dementia

Donate Body of Knowledge to an opponent that has two or more cards in hand, then deal nonlethal damage to it.
Body of Knowledge triggers, causing its controller to draw that many cards.
Orcish Bowmaster triggers for each card drawn. Resolve the first trigger, dealing 1 damage to Body of Knowledge and causing you to amass Orcs 1.
Repeat from step 2.

Target opponent loses the game

Infinite card draw for target opponent

Infinite draw triggers for target opponent

Near-infinite +1/+1 counters on a creature token

Body of Knowledge

Orcish Bowmasters

Donate control of Bloodcrazed Hoplite to an opponent.
Put a +1/+1 counter on Bloodcrazed Hoplite either by proliferating or by any other method.
Bloodcrazed Hoplite triggers, targeting any creature controlled by you or another opponent.
When the opponent commits that crime, Patrolling Peacemaker triggers, causing you to proliferate and put a +1/+1 counter on Bloodcrazed Hoplite.
Repeat from step 3.

Infinite proliferate

Patrolling Peacemaker

Bloodcrazed Hoplite

Give control of Blightbeetle to an opponent, if needed. Also, give Goblin Sharpshooter deathtouch, if needed.
Activate Goblin Sharpshooter by tapping it, dealing 1 damage to the additional creature and destroying it due to Goblin Sharpshooter's deathtouch.
When the creature dies, its undying ability and Goblin Sharpshooter trigger.
Resolve the creature's undying trigger, returning it from your graveyard to the battlefield without a +1/+1 counter on it due to Blightbeetle.
Resolve the Goblin Sharpshooter trigger, untapping it.
Repeat from step 2.

Blightbeetle

Mikaeus, the Unhallowed

Goblin Sharpshooter

Donate Blightbeetle to an opponent
Activate Woe Strider by sacrificing the undying creature.
When the undying creature dies, its undying ability triggers, returning itself from your graveyard to the battlefield without a +1/+1 counter on it due to Blightbeetle.
Resolve the Woe Strider ability.
Repeat from step 2.

Infinite scry 1

Undying Creature

Woe Strider

Combos with "Iroh, Tea Master"