Romana II + There and Back Again + Intruder Alarm

Romana II

There and Back Again

Intruder Alarm

How it works

1. At the beginning of your precombat main phase, There and Back Again triggers, putting a lore counter on it.
2. There and Back Again's third chapter ability triggers, creating a legendary 6/6 Smaug creature token and causing you to sacrifice There and Back Again.
3. When Smaug enters the battlefield, Intruder Alarm triggers, untapping all creatures.
4. Activate Romana II by paying 1 and tapping it, creating a token copy of Smaug with haste.
5. Put either Smaug token into your graveyard due to the legend rule.
6. Intruder Alarm and the Smaug token that died trigger.
7. Resolve the Intruder Alarm trigger, untapping all creatures.
8. Resolve the Smaug trigger, creating fourteen Treasure tokens.
9. Activate a Treasure by tapping and sacrificing it, adding 1.
10. Repeat from step 4.

This explosive loop begins when There and Back Again reaches its final chapter, creating the legendary dragon Smaug and triggering Intruder Alarm, which keeps all creatures primed to untap on command. With Intruder Alarm watching the battlefield, tapping Romana II to copy Smaug instantly triggers the legend rule; sending one legendary dragon to the graveyard unlocks a massive windfall of fourteen Treasure tokens. Sacrificing just one of those newly minted Treasures easily pays the activation cost for Romana II, leaving you with a surplus of mana while restarting the whole chain.