Tidespout Tyrant + Mana Crypt

Prerequisites

You control a nontoken permanent that can be cast using {C}{C}.

Steps

1. Cast Mana Crypt by paying its mana cost.
2. Tidespout Tyrant triggers, returning a nontoken permanent that can be cast using {C}{C} from the battlefield to your hand.
3. Activate Mana Crypt by tapping it, adding {C}{C}.
4. Cast the nontoken permanent returned in step 2 by paying its mana cost.
5. Tidespout Tyrant triggers, returning Mana Crypt from the battlefield to your hand.
6. Repeat.