Brundt also plays a role in Lunar Diplomacy. He provides players with a seal of passage which will allow them to visit Lunar Isle as a peaceful ambassador. Without a seal of passage, players will not be able to go to Lunar Isle, and talking to anyone on the Isle without a seal of passage will result in the player being teleported off the island. After completing Lunar Diplomacy, players are able to visit the island without the seal of passage, but will still be unable to talk to anyone. This changes after the player completes Dream Mentor, at which point 'Bird's-Eye' Jack becomes a banker on Lunar Isle, who will allow players to access their bank even without a seal of passage.
Brundt will replace seals of passage for free if a player loses or destroys it. Because of this, it is advisable for players who have not completed Dream Mentor to destroy their seal of passages when they are done with them. This is because if a player has a seal of passage in their bank, but forgets to bring it with them to Lunar Isle, there is no nearby bank to get it from, and since the seal of passage is in their bank, Brundt will not give them another one. Contrarily, if a player has destroyed their seal of passage, Brundt will give them one without necessitating a trip to a bank.