Marneus Calgar + The Watcher in the Water

Prerequisites

• You have a way to draw a card during an opponent's turn.
• You have a way to interrupt the loop after drawing your library.

Steps

1. 1Draw a card during an opponent's turn by triggering Marneus Calgar using his activated ability, or by any other method.
2. 2The Watcher in the Water triggers, creating a 1/1 Tentacle creature token.
3. 3When the Tentacle enters the battlefield, Marneus Calgar triggers, causing you to draw a card.
4. 4Repeat from step 2.
5. 5After drawing any number of cards, interrupt the mandatory infinite loop by winning the game or removing a combo piece in response to a trigger.

Effects

• Infinite card draw
• Infinite draw triggers
• Near-infinite creature tokens
• Near-infinite ETB