Marneus Calgar, and The Watcher in the Water

Prerequisites

• Marneus Calgar on the battlefield
• The Watcher in the Water on the battlefield
• 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
• available

Steps

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

Results

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