Bonus Round + Turnabout + Strionic Resonator

Bonus Round

Turnabout

Strionic Resonator

How it works

1. Cast Bonus Round by paying 1, creating an ability that will trigger each time a player casts an instant or sorcery spell this turn.
2. Cast Turnabout by paying 2.
3. When you cast Turnabout, the ability created by Bonus Round in step 1 triggers.
4. In response, activate Strionic Resonator by paying 2 and tapping it, copying the ability from Bonus Round.
5. Resolve the copied ability, copying Turnabout.
6. Resolve the copy of Turnabout, untapping Strionic Resonator and all other artifacts you control.
7. Activate artifacts you control by tapping them, adding at least 2.
8. Repeat from step 4 any number of times.
9. If you can add at least 3 in step 7, this combo produces infinite mana.