You have at least one legendary creature card exiled with a memory counter on it.
Arcane Adaptation on the battlefield with "Assassin" chosen.
Steps
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.
When the creature tokens enter the battlefield,
Blasting Station triggers that many times, untapping
Blasting Station.
Activate
Blasting Station by tapping it and sacrificing another legendary creature token except
Éomer.
When the creature dies,
Éomer triggers, untapping all creatures you control and causing you to get an additional combat phase after this one.