Lullmage Mentor + Intruder Alarm

Lullmage Mentor

Intruder Alarm

How it works

1. Whenever an opponent casts a spell, activate Lullmage Mentor by tapping seven Merfolk you control, countering that spell.
2. Lullmage Mentor triggers, creating a 1/1 Merfolk creature token.
3. The Merfolk token enters the battlefield, triggering Intruder Alarm, untapping all creatures.
4. Repeat.