Éomer, Marshal of Rohan | Kari Zev, Skyship Raider | Helm of the Host

(and one other card)

Helm of the Host attached to
Éomer.
Kari Zev does not have summoning sickness and cannot be blocked and killed by an opponent.

At the beginning of your combat phase,
Helm of the Host triggers, creating a nonlegendary token copy of
Éomer with haste.
Declare
Kari Zev as an attacker.
Kari Zev triggers, creating a legendary 2/1 Ragavan creature token that is tapped and attacking.
Holding priority, activate
Altar of Dementia by sacrificing Ragavan.
When Ragavan dies, each
Éomer that hasn't triggered this turn triggers, untapping all creatures you control and causing you to get at least one additional combat phase after this one.
Resolve the
Altar of Dementia ability, causing target player to mill cards equal to Ragavan's power.
Repeat each combat phase.