Halo Fountain + Phyrexian Altar + Karn, the Great Creator

Halo Fountain

Phyrexian Altar

Karn, the Great Creator

How it works

1. Activate Karn's first loyalty ability by putting a loyalty counter on it, causing Halo Fountain to become an artifact creature until end of turn.
2. Activate Halo Fountain's first ability by paying , tapping it and untapping it, creating a 1/1 Citizen creature token.
3. Activate Phyrexian Altar by sacrificing the Citizen, adding .
4. Repeat from step 2.