Declare Altaïr as an attacker. Altaïr triggers, exiling Éomer from your graveyard with a memory counter on it, and then creating a tapped and attacking token copy of each card you own that is exiled with a memory counter on it.
Activate Ashnod's Altar by sacrificing another legendary creature token except Éomer, adding CC.
When the creature dies, Éomer triggers, untapping all creatures you control and causing you to get an additional combat phase after this one.