Karn needs four more loyalty counters for you to activate his ultimate ability, which means that you’ll need to proliferate four times. You’ve only got three cards that are able to perform proliferation, however, so the question lies in where you’re going to get the fourth one you need.
- Tap two Seachrome Coasts for
(one used as generic mana), and three islands for (all used as generic mana). - Sacrifice Gore Vassal to put a -1/-1 counter on Janus’s Mad Auntie. The Mad Auntie is now a 3/1 creature (with Avarice Amulet attached).
- Spend
to cast Steady Progress. Add a loyalty counter to Karn Liberated and a -1/-1 counter to Mad Auntie. Karn Liberated now has 11 counters. The Mad Auntie is now a 2/0 creature and dies. You draw Glint Hawk. Avarice Amulet’s ability triggers and you gain control of it. - Spend to attach Avarice Amulet to Thrummingbird. Thrummingbird is now a 1/1 creature (with Cast Into Darkness and Avarice Amulet attached).
- Declare the start of your combat phase, assigning your Thrummingbird as an attacker. Janus has no creatures that can block it, so Thrummingbird deals 1 damage to him. Janus is now at 19 life.
- Thrummingbird’s ability triggers. Add a loyalty counter to Karn Liberated. Karn Liberated now has 12 counters.
- On your second main phase, tap three plains for
(two used as generic mana). - Tap Throne of Geth and sacrifice Avarice Amulet to activate the Throne’s ability. Add a loyalty counter to Karn Liberated. Karn Liberated now has 13 counters.
- Spend to cast Glint Hawk. When Glint Hawk enters the battlefield, choose to return Throne of Geth to your hand.
- Spend to cast Throne of Geth.
- Tap Throne of Geth and sacrifice itself to activate its ability. Add a loyalty counter to Karn Liberated. Karn Liberated now has 14 counters.
- Activate Karn Liberated’s third and ultimate ability by removing 14 loyalty counters.