Deucalion

"Know me? You've never seen anything like me. I am the Alpha of Alphas. I am the apex of apex predators! I am Death, destroyer of worlds! I am the Demon-Wolf! ~Deucalion"

"“Are you ready Jennifer? Hmm? Have you gathered your herbs? Prayed to your ancient gods and your oak trees? Slit a baby's throat perhaps? Should we show them why you needed to sacrifice 9 innocent people just to face me? Or is it 12 now?” — Deucalion to Jennifer when he is shifting in Lunar Ellipse"

Deucalion is the secondary antagonist turned anti-hero of Season 3A of Teen Wolf. He is the blind leader of The Alpha Pack, and refers to himself as the "Alpha of Alphas". In spite of his blindness, he refers to himself as a man of vision. He is introduced as the season's main antagonist but eventually forms an alliance with the heroes after he is outranked by the true main villain.

He is potrayed by Gideon Emery.

Backstory
He was once an Alpha werewolf who had a vison of peace between werewolves and hunters. He was warned not to follow through his plan by Talia Hale, a well respected Alpha.

Irregardless, he and his pack met with a group of hunters, led by Gerard Argent. Several other hunters also believed peace was possible and for this Gerard led the pack and the hunters into a death trap. Gerard kills off Deucalion's pack and his own henchmen. Gerard only wounds Deucalion and tells him that he was short sighted, and that he will be blamed for the deaths. To further hurt Deuclaion, he stick two flashbang arrows in his eyes, blinding the werewolf.

Deucalion lived, but because of his blindness, his Beta, Marco, saw him unfit to be an Alpha and tried to kill him. Deuclaion, manages to kill Marco and realizes he can take power from killing his Beta's and with a new cynical look on the world, he killed off his own pack.

Soon after he formed the Alpha pack, with Ennis, Kali, and twins Ethan and Adien, of whom he got to kill off thier packs.

Reign in Beacon Hills
He learned of the Alpha, Derek Hale, Talia's son, in Beacon Hills and made his way to the town with the Alpha Pack. Shortly after arriving, they adbuct Boyd and Erica, two of Derek's Beta's, and they also held Derek's long lost sister Cora hostage. During their time in captivity, Erica is killed by Kali. Eventually, series protagonist, Scott McCall and Derek team up and manage to rescue Boyd and Cora, discovering Erica's body.

It's later revealed Deucalion isn't really after Derek, but Scott. It turns out Scott is the rarest of werewolves, a "true Alpha", a werewolf who's Alpha powers are unlocked through character and willpower, not conquest and murder like most Alpha's. Deucalion wants Scott to join his pack for his True Alpha powers, even though it's clear Decualion will kill to absorb his packs powers, and shown with Ennis.

As it turns out, a supernatural serial killer, known as the Darach, is killing people in Beacon Hills, Deucalion takes interest, and searches for the Darach as well. It turns out the Darach is Julia Barccari, who was living under the name Jennifer Blake. Julia is Kali's emissary, who was left for dead in Deucalion's conquest of the Alpha's former packs. When Julia abducts Scott's mother, his best friends father, and girlfriends father, Deucalion forces Scott to join him offering to find the parents.

In the mid season finale, Deucalion and Scott confront Julia in her hidout, along with Derek. Deucalion shifts into a demonic looking werewolf form and easily overpowers Derek. Julia beats Deucalion to a pulp and restores his eyesight. Deucalion tries to force Scott to kill Julia, and Julia protects herself with a mountain ash circle, which Scott eventually overpowers, becoming an Alpha at last. Astonished, the distracted Julia's throat is slashed by Deucalion. Scott and Derek leave after, they tell Deucalion that they will let him live if he redeems himself, if not, then even with his new eyesight, he won't see them coming.

After the Alpha Pack
Deucalion later hired Breaden to rescue Derek from a family of Mexican hunters.