The Spectral Jeweller
Note: The following content was in a former version of Pixelmon and is no longer accessible.
The Spectral Jeweller is a special Halloween NPC that resembles a Haunter, although it is colored red. It can be spawned using the "/halloween" command. Normally, the Spectral Jeweller will despawn under normal conditions (being far away from all players), but the Spectral Jeweller can be prevented from despawning by using the command, "/halloween persistent".
Upon interacting with the Spectral Jeweller, it will state, "I'm here to exchange your hallowed gems!". These "hallowed gems" refer to seventeen different Gems (one for each type except Fairy Gems) that each are found in different Gem structures, which spawn in different biomes that correspond to each type. Unlike normal Gems, the Gems found in these Gem structures are prefixed with "Hallowed" (e.g., "Hallowed Dragon Gem"). Each hallowed Gem can be used on the Spectral Jeweller to give them to it, and if all seventeen types of hallowed Gems are given to the Spectral Jeweller, the player will be rewarded with an Egg containing a Misdreavus. After completing the Spectral Jeweller's task, the player cannot redo the task in the same world, even if multiple Spectral Jewellers are spawned.
Unlike other Pokémon, the Spectral Jeweller cannot be engaged in battle or captured. However, if the player is one of the winners of the Halloween 2014 contest on the Pixelmon forums, using the /redeem command and specifying a party slot number containing a Haunter will cause that Haunter to have a special texture with the Spectral Jeweller's appearance.