Kotis, Sibsig Champion + Altar of Dementia + Eternal Witness

3-card combo · BGU

Verdict

Yes — this loop chains near-infinite extra turns through Kotis, Sibsig Champion's escape clause on Eternal Witness, turning a single extra turn spell into a lock.

Cards required

Cheapest stack total

$1.17

Color identity

BGU

Popularity

1,497 decks

Format

Commander

Buy required cards on TCGplayer

The engine requires Kotis, Sibsig Champion on the battlefield to grant Eternal Witness escape, letting it recur from the graveyard by exiling three other cards each loop. Altar of Dementia mills into the exile fodder needed for the next Eternal Witness cast, while each Eternal Witness trigger returns the extra turn spell — Time Warp or Temporal Manipulation are the cleanest targets — to hand. The table sees a Sultai shell with a heavy graveyard subtheme assembling what amounts to an indefinite turn lock.

How it works

Prerequisites

You have enough mana available each turn to cast the extra turn spell and enough mana each extra turn to cast Eternal Witness. You have not cast a spell using Kotis Extra Turn Spell - GY on Resolution

Steps

Cast the extra turn spell by paying its mana cost, causing you to take an extra turn after this one.
Move to your extra turn.
Activate Altar of Dementia by sacrificing Eternal Witness, causing you to mill cards equal to Eternal Witness's power.
Cast Eternal Witness from your graveyard by paying its mana cost and exiling three other cards from your graveyard, ensuring not to exile the extra turn spell.
When Eternal Witness enters the battlefield, it triggers, returning the extra turn spell from your graveyard to your hand.
Repeat.

Result

Near-infinite turns; Lock

Cheaper, tighter, alternate lines

Time Warp is the tightest extra turn spell here at 3UU with no downside, but Temporal Manipulation or even Walk the Aeons function identically. If Altar of Dementia is removed, any sacrifice outlet that mills or fills the graveyard fast enough — Altar of the Brood or a fetchland-heavy land package — can keep exile fodder flowing for the Eternal Witness escape cost.