Mirrormade | Estrid's Invocation | Oblivion Ring

(and one other card)

Mirrormade and
Estrid's Invocation in hand.
Oblivion Ring and
Altar of the Brood on the battlefield.
({3} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) available.

Cast
Mirrormade by paying ({2} magic symbol) ({U} magic symbol) .
Mirrormade enters the battlefield as a copy of
Oblivion Ring, triggering
Altar of the Brood and itself.
Resolve the
Altar of Brood trigger, causing each opponent to mill a card.
Resolve the
Mirrormade's trigger, exiling
Oblivion Ring.
Cast
Estrid's Invocation by paying ({2} magic symbol) ({U} magic symbol) .
Estrid's Invocation enters the battlefield as a copy of the
Oblivion Ring copy, triggering
Altar of the Brood and itself.
Resolve the
Altar of Brood trigger, causing each opponent to mill a card.
Resolve the
Estrid's Invocation's trigger, exiling
Mirrormade.
Mirrormade leaves the battlefield, triggering itself, returning
Oblivion Ring from exile to the battlefield.
Altar of the Brood and
Oblivion Ring trigger.
Resolve the
Altar of Brood trigger, causing each opponent to mill a card.
Resolve the
Oblivion Ring trigger, exiling
Estrid's Invocation.
Estrid's Invocation leaves the battlefield, returning
Mirrormade from exile to the battlefield.
Repeat from step 2 until each opponent has an empty library, then end the loop by choosing to copy or exile any other permanent.