Medomai the Ageless | Idris, Soul of the TARDIS | Karn's Bastion

(and one other card)

Idris in hand.
All other permanents on the battlefield.
An opponent cannot block creatures you control.
Medomai the Ageless has at least one +1/+1 counter on it.
({1} magic symbol) ({U} magic symbol) ({R} magic symbol) available the first turn, with ({4} magic symbol) each extra turn available.

Deal combat damage to an opponent using
Medomai the Ageless.
Medomai the Ageless triggers, causing you to take an extra turn after this one.
Cast
Idris by paying ({1} magic symbol) ({U} magic symbol) ({R} magic symbol) .
When
Idris enters the battlefield, it triggers, exiling
Medomai the Ageless until
Idris leaves the battlefield.
Move to your extra turn.
At the beginning of your upkeep,
Idris's vanishing ability triggers, removing a time counter from it.
Activate
Karn's Bastion's second ability by paying ({4} magic symbol) and tapping it, putting a time counter on
Idris.
Deal combat damage to an opponent using
Idris.
Idris triggers, causing you to take an extra turn after this one.
Repeat from step 5.