Lita, Mechanical Engineer + Strionic Resonator + Karn, the Great Creator

Lita, Mechanical Engineer

Strionic Resonator

Karn, the Great Creator

How it works

1. Activate Karn by putting a loyalty counter on them, causing Strionic Resonator to become an artifact creature until end of turn.
2. At the beginning of your end step, Lita triggers.
3. In response, activate artifact creatures by tapping them to add at least 3.
4. Continuing to hold priority, activate Strionic Resonator by paying 2 and tapping it, copying Lita's triggered ability.
5. Resolve the copied ability, untapping all artifact creatures you control.
6. Repeat from step 3.