Activate Opposition by tapping an untapped creature you control, tapping a creature an opponent controls.
Hylda of the Icy Crown triggers, holding priority, activate Ashnod's Altar by sacrificing the creature tapped in step 1, adding {C}{C}.
Resolve the Hylda of the Icy Crown trigger, causing you to pay {1} to create a 4/4 Elemental creature token.
Repeat.
You may also repeat this loop during each turn.

Tap all creatures opponents control during each turn

Hylda of the Icy Crown

Opposition

Ashnod's Altar

Activate Opposition by tapping Stonybrook Schoolmaster, targeting Stonybrook Schoolmaster.
Stonybrook Schoolmaster triggers, creating a 1/1 Merfolk Wizard creature token.
The Merfolk Wizard enters the battlefield, triggering Intruder Alarm, untapping all creatures.
Resolve the Opposition ability, tapping Stonybrook Schoolmaster.
Stonybrook Schoolmaster triggers, creating a 1/1 Merfolk Wizard creature token.
The Merfolk Wizard enters the battlefield, triggering Intruder Alarm, untapping all creatures.
Repeat.

Infinite creature tokens

Infinite ETB

Infinite mana creatures you control can produce

Infinite untap of all creatures

Intruder Alarm

Stonybrook Schoolmaster

Activate Opposition by tapping an untapped creature you control, tapping a creature an opponent controls.
Verity Circle triggers, causing you to draw a card.
Activate Mind over Matter by discarding a card, untapping a creature you control.
Repeat.
You may also repeat this loop during each turn.

Verity Circle

Mind Over Matter

Activate Opposition by tapping an untapped creature you control, tapping a creature an opponent controls.
Hylda of the Icy Crown triggers, holding priority, activate Phyrexian Altar by sacrificing the creature tapped in step 1, adding {1}.
Resolve the Hylda of the Icy Crown trigger, causing you to pay {1} to create a 4/4 Elemental creature token.
Repeat.
You may also repeat this loop during each turn.

Phyrexian Altar

During an opponent's turn, activate Opposition by tapping a blue creature you control except Unctus.
The creature triggers, causing you to loot.
The Watcher's first ability triggers, creating a 1/1 Tentacle creature token.
Resolve the Opposition ability.
Repeat.

Infinite self-discard triggers

Near-infinite ETB

Infinite draw triggers

Infinite looting

Near-infinite tapped creature tokens

Unctus, Grand Metatect

The Watcher in the Water

Activate Opposition by tapping Emmara, targeting Emmara.
Emmara triggers, creating a 1/1 Soldier creature token.
The Soldier enters the battlefield, triggering Intruder Alarm, untapping all creatures.
Resolve the Opposition ability, tapping Emmara.
Emmara triggers, creating a 1/1 Soldier creature token.
The Soldier enters the battlefield, triggering Intruder Alarm, untapping all creatures.
Repeat.

Emmara, Soul of the Accord

Activate Opposition by tapping Warchanter Skald, targeting Warchanter Skald.
Warchanter Skald triggers, creating a 2/1 Dwarf Berserker creature token.
The Dwarf Berserker enters the battlefield, triggering Intruder Alarm, untapping all creatures.
Resolve the Opposition ability, tapping Warchanter Skald.
Warchanter Skald triggers, creating a 2/1 Dwarf Berserker creature token.
The Dwarf Berserker enters the battlefield, triggering Intruder Alarm, untapping all creatures.
Repeat.

Combos with "Opposition"