@4:44, no idea why they milled the Through the Breach. It does nothing for you, lol. Maybe they're a newer Lantern player? @10:30, this is a clear mistake on the Lantern pilot's part. They need that Thoughtseize to make sure they can clear your hand. You've already demonstrated that you don't have the other main threats to the deck in hand (Karn, Ring, or Boseiju), so that only leave something like Ulamog (which you do happen to have). You were clearly telegraphing the Ulamog. If they wait to get another black mana, they Thoughtseize you and then the lock is complete.
@4:44, no idea why they milled the Through the Breach. It does nothing for you, lol. Maybe they're a newer Lantern player?
@10:30, this is a clear mistake on the Lantern pilot's part. They need that Thoughtseize to make sure they can clear your hand. You've already demonstrated that you don't have the other main threats to the deck in hand (Karn, Ring, or Boseiju), so that only leave something like Ulamog (which you do happen to have). You were clearly telegraphing the Ulamog. If they wait to get another black mana, they Thoughtseize you and then the lock is complete.