Hex

Hex is a self-proclaimed "Master Magician" who desires to rule the world with his magic powers and currently lives in a large tower-like place.

Hex has a niece named Charmcaster who is mostly with or around him because her father Spellbinder was murdered by Adwaita. He once possessed five magical, mystical charms called the Charms of Bezel, from the interdimensional realm of Bezel, that give him the immense powers and abilities of levitation, fire, reincarnation, lightning, and luck, in addition to his own spell-casting abilities.

Hex is more of an enemy to Gwen than he is an enemy to Ben, as he attacks her in all his appearances except in Don't Drink the Water, and shows more hate and rancor towards her, as seen in Tough Luck, he clearly states he wants to get revenge on Gwen, not Ben.

Powers and Abilities
Hex is a vastly skilled magician that can manipulate the forces of magic for many feats. Such as levitation, manipulating energy for blasts and shields, telekinesis, clairvoyance, elemental control (fire, lightning, earth, etc.), bringing inanimate objects to life, teleportation, summoning stone creatures, etc.

Hex usually channels his powers through his staff, which can only be used by a "master magician".

Hex briefly possessed the Charms of Bezel before Gwen destroyed them.

In addition to his magical abilities, Hex is also very agile.

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, 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 (who is revealed to have been possessed by Zs'Skayr) appears in Ben 10: Protector of Earth, as a boss that Ben faces at the end of Effigy Mounds. Zs'Skayr claimed he was using Hex's power to open a portal to his home world and bring his army to earth.

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 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, 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. No 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 debut on Ben 10: Ultimate Alien in the episode The Enemy of My Frenemy where he captures Gwen in a force bubble who was 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 Adwaita. Hex says that while he loves his niece, he is not about to go on a "suicide mission" and go back to help her. 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 Dream Eater's effects on him.

Ben 10

 * Lucky Girl (first appearance)
 * Tough Luck
 * Don't Drink the Water

Ben 10: Alien Force

 * Time Heals (first re-appearance)

Ben 10: Ultimate Alien

 * The Enemy of My Frenemy (first re-appearance)
 * Night of the Living Nightmare (dream)

Ben 10: Protector of Earth
Hex is a Mini Boss, he was possessed by Zs'Skayr in the battle.

Ben 10 Alien Force: Vilgax Attacks
Hex didn't appear, but he is mentioned by Charmcaster, stating that Ben has got a lot of nerve facing her after what he did to her uncle.

Ben 10 Alien Force: The Rise of Hex
Hex is the Main Antagonist.

FusionFall
Hex appears in Fusion Fall to destroy planet fuse as Ben's ally since they have a truce. His staff is a weapon for the players.

Trivia

 * According to Dwayne:
 * Hex raised Charmcaster.
 * Charmcaster's intentions were to return to Ledgerdomain and save her people, ruling the world was Hex's goal, not Charmcaster's.
 * Hex was born and raised in Ledgerdomain.
 * Hex did try to defeat Adwaita, for years.
 * According to Ben 10 Pop-Up Edition, Hex's facepaint is an homage to the masks that the warriors of Bezel wore.
 * When Hex turns into a baby at the end of Don't Drink the Water, he has similar looks to toddler Ben.
 * Hex's name is pronounced the same way as the Dutch word 'heks' that means 'witch'.
 * Hex made a cameo in The Secret Saturdays, being one of the faces shown in the criminal database.
 * Hex's name comes from the word 'Hex' which means a spell.