The Evil Monster appeared in "Dad's Dungeon." It is the last trial in Joshua's Dungeon. It is very large and evil. It seems to be invulnerable except by being stabbed in its eye. It laughs hysterically whilst attacking. The monster seems to be the one who killed Joshua, as one of his last messages on the Holo-Message Player shows him being pulled into the chamber where it was, while he was explaining that he was almost done working on the trial. This doesn't seem to be the case though, as Joshua is seen to be alive in Jake's memory in Crystals Have Power, in which Jake was older (not a baby). Joshua also explained that he was going to trap it in the pit in the chamber, but appearantly failed.
It is a giant monster with many green spikes sticking out of its back. It's body is very long and serpintine, and has tentacles sticking out of its body that seem to end with green spikes, thgough some don't. It has long, skinny arms. Its left wrist has the key to unlock Jake's Family Sword chained around it and one of the fingers has a spike on it. Its teeth are also similar to those of a Lub Glub. It has one eye that seems to look like a crystal with a pentagram inside. The eye shines when stabbed.