Stalwart Successor + Bloodflow Connoisseur + Grazing Kelpie

Stalwart Successor

Bloodflow Connoisseur

Grazing Kelpie

How it works

1. Activate Bloodflow Connoisseur by sacrificing Grazing Kelpie
2. When Grazing Kelpie dies, its persist ability triggers, returning it from your graveyard to the battlefield with a -1/-1 counter on it.
3. When Grazing Kelpie enters, Stalwart Successor triggers, putting a +1/+1 counter on Grazing Kelpie
4. Resolve the Bloodflow Connoisseur ability.
5. Repeat.