All 25 Combos with Arcbound Condor

Eirdu, Carrier of Dawn // Isilu, Carrier of Twilight + Ashnod's Altar + Arcbound Condor

Infinite Mana: Infinite LTB, Infinite ETB, Infinite sacrifice triggers, Infinite death triggers, Infinite colorless mana, Infinite +1/+1 counters on certain creatures

Activate Ashnod's Altar by sacrificing Arcbound Condor. When Arcbound Condor dies, its modular ability and persist ability trigger. Resolve the modular trigger, putting Arcbound Condor's +1/+1 counters on another artifact creature. Resolve the persist trigger, returning Arcbound Condor from your graveyard to the battlefield. It will not have a -1/-1 counter on it due to its modular ability. Repeat.