Hex's History
Prior to Ben 10
Hex was born and raised in Ledgerdomain. He tried to defeat Addwaitya for years, but remained unsuccessful.
Ben 10
In Lucky Girl, Hex attempts to steal an ancient spell book known as the "Archamada Book of Spells", dating back to the 16th century and containing powerful spells that, combined with the Charms of Bezel, gives the user unimaginable powers. However, the Charm of Luck falls into Gwen's possession during Hex's fight with XLR8, and she soon learns to utilize its power. Despite Hex's attempts to reclaim the Charm of Luck and the Spellbook, he is eventually defeated by the Tennysons in a graveyard and arrested, while Gwen destroys the Charms.
Hex returns in Tough Luck; his niece Charmcaster breaks him out of prison. Together, they search for the Keystone of Bezel, which he plans to use to recreate the other five Charms and multiply his power tenfold. Again, Gwen gets the Keystone and is soon attacked by the pair. Hex fails again due to both the Tennysons interference and Charmcaster betraying him so she can take the Charms for herself (though she fails as well).
Hex then reappears in Don't Drink the Water, having aged into an old man since his last appearance. Learning of the Fountain of Youth, he tracks it down and uses it to become immortal. However Ben, reduced to a toddler by the effects of the Fountain, uses young Heatblast to try and evaporate the Fountain when, due to being taunted by Gwen, he has a very bad tantrum and goes supernova hot, allowing him to evaporate the water, which overexposes Hex to it and reduces him to an infant. Hex is last seen in Charmcaster's hands, where his niece enjoys taunting him in his infant state.
Alien Force
Hex has seemingly made up with his niece, and now lives in a tall, Japanese-style mansion where he keeps all his books of magic, including the Archamada. He has returned to his original age, and his look is mostly the same than before, though his clothes are now fully red instead of black and red, and his face is whiter than before, making it look more like a skull.
In Time Heals, Gwen infiltrates his home to steal the Grimoire of Archamada, and, despite Paradox's warning, uses it to time travel to the past and stop Ben and Kevin from hacking the Omnitrix and preventing Kevin's mutation. Though she succeeds, her action causes Hex to be able to take over the world. Thanks to his magic, Hex knows that Gwen is responsible for the creation of this future, and tries to prevent her from turning the future back to normal. However, after a short fight against Charmcaster and a possessed Kevin, Gwen finds the prison and frees Ben who helps her get back the Grimoire of Archamada and gain enough time to go back in the past and prevent herself from changing the future.
Ultimate Alien
Hex makes his reappearance in the episode Enemy of My Frenemy, where he captures Gwen in a force bubble during her attempt at stealing another book and has her at his mercy. Gwen explains that she wanted to help Charmcaster who is in Ledgerdomain, and, concerned about Charmcaster, he lets her out. Gwen wanted him to work with her to help Charmcaster because the last time she saw her was that she was fighting against Addwaitya. Hex says that while he loves his niece, he is not about to go on a "suicide mission". Hex lets Gwen take the spell book and whatever she needs if she leaves him in peace.
Hex then makes an appearance in Night of the Living Nightmare as a dream character that attacks Ben due to Albedo and the Cassiopeian Dream Eater's effects on him.
Omniverse
In Charm School, Hex appears again as a Professor at Friedkin University. Hex is revealed to be the magical artifacts and antiquities professor and the favorite teacher of Gwen Tennyson. It seems like the two of them are over their conflictions. He was attacked by Ben Tennyson who hadn't known about his change. Hex tells him that he can only teach here because he gave every single one of his magical artifacts to the university. After hearing about his niece's return, he tells Gwen and the others that her troubled past deeply damaged her, but that he knows that she is still good deep down and can be saved.
When he meets Charmcaster, he offers her to stay with him and be a part of his life. However, Charmcaster double-crosses him and almost turns Hex into a totem in her quest to obtain his staff. However, all this happened in his library where he was practically invincible, forcing Charmcaster to retreat. Later, Charmcaster manages to fulfill her plans and sneak attacks him disguised as Xagliv, turning Hex into a totem and using his powers to find his staff. At the end of the episode, he, Charmcaster, and the other totems were sent back to Ledgerdomain by Gwen, who later inherited Hex's library.
In Third Time's a Charm, it is shown that Hex as a totem, when in Charmcaster's magical bag, is free to move and speak as normal except reduced in size. He has a very antagonistic relationship with Addwaitya and Darkstar inside the bag, since Addwaitya murdered his brother and Darkstar broke his niece's heart. Thanks to Ben and Gwen, Hex is ultimately freed from being a totem and is immediately greeted with a hug by Professor Xagliv, much to his dismay. Charmcaster, now a stone totem herself, is kept in his and Gwen's custody under the hope that she can get better someday.
Hex reappears in The Most Dangerous Game Show, where the first round of Charles Zenith's game show is held in his library. Hex appears in a puff of smoke to anyone who talks in the library, making a shushing noise at them when he does. When he does this to Jennifer Nocturne, she shushes him right back indignantly. Interestingly, Hex shows no concern that Charmcaster is present, which suggests the two have made up with one another again possibly during his imprisonment in her bag.
