Jude is the final boss of the first two Witch Spring games, and is the instigator of the events of the third game despite never making an on-screen appearance.
For hundreds of years, Jude served as Aramute's secretary. Feeling that he wasn't being properly rewarded for his efforts, though, he hatched a plot to take over Lord Aramute's role and take Aramute's power for himself. He informed the Pope about (what he thought was) the secret of the Springs and convinced Pope to start a war on the deities. Disguised as Crown, the best Warrior in Vavelia, Jude was an active participant in killing the Temple Lords.
Ten years later, Jude remains disguised as Crown when Pieberry and Luna's stories begin. He first encounters Pieberry when she visits Elysion Temple, where he fights her. When he injures her, Black Joe steps in and is temporarily returned to his original Nuuk form after Jude hits him. With his original power restored, Black Joe knocks off Jude's helmet, revealing him to be a deity to Pieberry. He lies about his disguise and motives for attacking her, and convinces her that he was working undercover to undermine the Pope.
While Luna sees him a handful of times during the course of the game, he doesn't notice her until she encounters him in Durok Temple. He attacks her, though she overpowers him after a battle. Having sensed Aramute's power in him, however, she mistakes him for Aramute himself. Jude takes advantage of this, convincing her to train hard and gather more magic power for him before they infiltrate the Pope's Castle. After they get in, however, Jude tricks her into standing in a magic circle that sucks out her magical power, leaving her helpless. He has her imprisoned afterwards, though she is able to escape via a small opening in her cell wall.
In the meantime, Pieberry has made her way into Durok Temple, and manages to restore his Spring. However, as she is about to open the chest in his temple, she is ambushed by troops sent by Jude (in the first game) or Jude himself (the second game) and is knocked unconscious. She, too, is locked up in prison. However, Jude unlocks her cell to set her free in the hopes that she would take out the Pope so he could set her up as the "evil witch." His plan nearly works, except that he is defeated by Pieberry (first game) or a tag-team of Pieberry and Luna (second game). Afterwards, the dark magic stones he consumed for the sake of gaining power force him to revert to his true form as an Ancient Dragon.
Breaking out of the palace, he terrorizes the citizenry of Vavelia Village before he was intercepted. In the first game, only Temar and the reawakened Temple Lords stop him, with Aramute destroying him completely. In the second game, the two keep their original involvement, but depending on the friendships Luna forms during the game, the Nuuks, Sofia with long-range artillery, the dwarves and their cannons, Red Beard, and Ludina will all intervene to save the village.
Witch Spring 3 sheds some more light on Jude's past.
Long before the start of the story, he was one of the Ancient Dragons. However, he became the Guardian Animal of Aramute and was given the powers of a deity, so he was no longer beheld to the Dragon's Nest for immortality like the rest of his kind. As a result, he conspired to use the Ancient Dragons to help him instigate the Spring War on Vavelia. He stole the Dragon's Nest and gave it to Regal, telling Regal that the Dragon's Nest had the power to heal, so Regal would try to use it to heal Esther when it was actually absorbing her vitality instead. The Ancient Dragons flew to Shubeth to recover the Dragon's Nest, but Regal (and Jude) had anticipated this. Regal called upon the aid of Vavelia's deities—and they sent Temar, a Maegrik Dragon and the strongest Guardian Animal of Vavelia's deities.
With Temar away, Jude was able to slay the Temple Lords and start the Spring War. Meanwhile, the Ancient Dragons found that Jude had tied the Dragon's Nest to Regal's life. If Regal died, so would the Dragon's Nest, but Regal would not be affected if the Dragon's Nest was destroyed. Thus, the Ancient Dragons could do little but assist him to ensure the Nest's safety.
Towards the end of Chapter 4 on the Light/True paths, Luna and Pieberry travel to Derkarr to reveal that both the Pope and Jude have died, and to expose their evils to the neighboring continent, as Vavelia's king also ruled over Derkarr. With Jude dead, the magic binding the Dragon's Nest to Regal also disappeared. Once Monnet realizes that the two Vavelian deities spoke the truth, she fatally wounded Regal and then left.
In Witch Spring 3's post-game, it is revealed that Jude was also Monnet's father, conceiving her with a human woman; this is why Monnet can transform into a human form and has a tiny hint of a deity's powers within her.