Basri's Lieutenant + Renata, Called to the Hunt + Phyrexian Altar

Basri's Lieutenant

Renata, Called to the Hunt

Phyrexian Altar

How it works

1. Activate Phyrexian Altar by sacrificing a creature with at least one +1/+1 counter, adding one mana of any color.
2. Basri's Lieutenant trigger, creating a 2/2 Knight token.
3. When Knight token enters the battlefield, Renata trigger, putting a +1/+1 counter on Knight token.
4. Repeat.