Dipper's black light

Dipper's black light is a portable black light that Dipper Pines carries around with him in order to read secret passages hidden in the journal.

History
After reciting an incantation from the journal in an attempt to prove to Agent Powers and Agent Trigger that its contents are real, Dipper raises the undead. With no way to defeat them, he and Mabel retreat into the Mystery Shack, and eventually meet up with Stan. The three are forced to hide themselves in the attic and baricade the door to keep the undead out. Dipper then searches the journal once more, even though it said that the undead were undefeatable. However, under the UV-A rays of the black lights set up for the party, a hidden passage is revealed, having been written in invisible ink.

After the events of the undead invading the Mystery Shack, Dipper is approached by Pacifica Northwest, who asks for his assistance in stopping the haunting at the Northwest Manor. While in the manor and cornered in by the ghost, realizing that it is a Category 10, he looks through the journal and gets to the passage on Category 10 ghosts. Underneath the "advice" column, nothing is written, but Dipper pulls out a portable black light he had been carrying with him in order to reveal the hidden contents. Unfortunately, the only thing that is written is, "Pray for mercy!"