Thran Dynamo + Umbral Mantle + Xenic Poltergeist

Thran Dynamo

Umbral Mantle

Xenic Poltergeist

How it works

1. Activate Xenic Poltergeist by tapping it, targeting Thran Dynamo.
2. Activate Umbral Mantle's equip ability by paying 0, attaching it to the Thran Dynamo.
3. Activate Thran Dynamo by tapping it, adding CCC.
4. Activate Umbral Mantle by paying 3 and untapping it, giving itself +2/+2 until end of turn.
5. Repeat.