Intruder Alarm + Deeproot Pilgrimage + Firdoch Core

Intruder Alarm

Deeproot Pilgrimage

Firdoch Core

How it works

1. Activate Firdoch Core's first ability by tapping it, adding one mana of any color.
2. Deeproot Pilgrimage triggers. Holding priority, activate Firdoch Core's second ability by paying 4, causing it to become a 4/4 artifact creature until end of turn.
3. Resolve the Deeproot Pilgrimage trigger, creating a 1/1 Merfolk creature token.
4. When the Merfolk enters the battlefield, Intruder Alarm triggers, untapping all creatures.
5. Activate Firdoch Core's first ability by tapping it, adding one mana of any color.
6. Deeproot Pilgrimage triggers, creating a 1/1 Merfolk creature token.
7. Repeat from step 4.