Requires

Marneus Calgar must be on the battlefield. The Watcher in the Water must be 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. Mana needed:

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