Intruder Alarm + Maskwood Nexus + Tough Cookie

Intruder Alarm

Maskwood Nexus

Tough Cookie

How it works

1. Activate Tough Cookie's first ability by paying 2, causing Maskwood Nexus to become a 4/4 artifact creature until end of turn.
2. Activate any number of mana-producing creatures you control by tapping them, adding at least 3.
3. Activate Maskwood Nexus by paying 3 and tapping it, creating a 2/2 Shapeshifter creature token.
4. When the Shapeshifter enters the battlefield, Intruder Alarm triggers, untapping all creatures.
5. Repeat from step 2.
6. If creatures you control can tap to produce at least 4, this combo nets infinite mana.

By turning Maskwood Nexus into a 4/4 artifact creature with Tough Cookie's animation ability, it becomes a legal creature subject to the battlefield-wide untap trigger of Intruder Alarm. Every time you pay {3} to activate Maskwood Nexus and birth a fresh 2/2 Shapeshifter, Intruder Alarm sees the creature enter and untaps your entire board in response. As long as your tapped mana-producers can generate enough juice to fund the Nexus's activation cost and any extra spent on Tough Cookie's initial animation, the loop sustains itself indefinitely—yielding infinite creature tokens, infinite entry triggers, and endless untaps for all your creatures.