Addwaitya

Adwaita is one of Ben 10's villains, an evil mystic being considered as the most powerful sorcerer in the Universe. He was was slightly mentionned in introduced in Ultimate Alien episode Where the Magic Happens, and is responsible for the death of Spellbinder, Gwen's rival Charmcaster's father, as well of Charmcaster's and her uncle Hex's villainous acts.

Though not directly stated or shown in the serie, it has been suggested that Adwaita was a Geochelone Aerio, from the same specie than Galapagus, one of the five Andromeda aliens Aggregor was looking for : he share's Galapagus' turtle-like appearance, and was mentionned by Galapagus in Escape from Aggregor ("Thanks Adwaita, it worked !"). Aggregor also stated in Map of Infinity that Galapagus' specie couldn't be hurt by mana, suggesting they have an affinity with it and explaining Adwaita's might.

Appareance
He is a turtle-like creature with pink fire-like energy surrounding his head.

Story
Adwaita's origin is unknown. At some point, he got his hands on the Alpha Rune, a powerful magic item (who was actually a piece of the Map of Infinity in disguise) and reach the Ledger Domain in an attempt to conquer it most likely he got corrupted by the power the artifact possess. The inhabitants of the dimension, though powerful sorcerers, were unable to defeat, and their leader, Spellbinder, had to send his brother Hex and daughter Charmcaster on Earth in order to keep them safe. Few time after that, Adwaita killed Spellbinder and took control of the Ledger Domain as a ruthless dictator.

Ben 10: Ultimate Alien
Adwaita was first introduced in Where the Magic Happens, when the Osmosian villain Aggregor reached his dimension in order to get his hand on the Alpha Rune. Chasing him, Ben, Kevin and Gwen were forced to ask for Charmcaster's help in order to reach the Ledger Domain. When the group arrived, Adwaita immedialty felt their presence, and, inraged by the intrusion, attacked them. The heroes quickly had to forget Aggregor in order to get rid of the evil sorcerer, and ended up teaming up against him. After a feral fight, Adwaita was surprised and distracted by an attack from Ultimate Humongousaur, allowing Aggregor to knock him out with a sneak attack and take the Alpha Rune from him before escape. The Ledger Domain then started falling apart, and Charmcaster, seeing Adwaita weakened, choosed to stay behind to fight him and save her people.

Trivia

 * Adwaita was mentioned on Escape From Aggregor by Galapagus ("Thank Adwaita it worked!"). On a related note, he closely resembles a Geochelone Aerio like Galapagus and Terraspin, as well, although displayed no sign of wind manipulation abilities nor the Chest Cavities of Geochelone Aerios that produce said wind nor the immunity to mana that all Geochelone Aerios have.
 * Adwaita was named after a tortoise from a Indian Zoo that lived to be 255.