Arcane Bombardment + Time Warp + Clockspinning

Arcane Bombardment

Time Warp

Clockspinning

How it works

1. Cast Clockspinning with buyback by paying 3.
2. Arcane Bombardment triggers, exiling an instant or sorcery at random from your graveyard, and casting a copy of Time Warp without paying its mana cost.
3. Resolve Time Warp, causing you to take an extra turn after this one.
4. Resolve Clockspinning, returning Clockspinning to your hand.
5. Repeat each turn.