Sep 23, 2021 · Guide to Warp Door Introduction The Warp Door is a mysterious door in Deltarune. It can be used to fast travel the party to other areas, which include the Field, Bake Sale, Forest, and Card Castle. Gameplay-wise, it functions similarly to the transportation by the River Person in Undertale.. Sep 22, 2021 · Secret Boss. When the glowing door is unlocked, return to trash heap. The NPC will guide you to the next step on the path to finding it. In the room in the mansion that seems like it obviously has a secret, there’s a switch on an object to interact with. (I’m not sure how you’re really meant to find it other than randomly poking everything.).