"You and me Derek, or they tear her apart. What do you say? You think you can beat me one on one?" - Kali to Derek Hale
Kali was, prior to the series, an alpha, the head of her pack and her love Julia Baccari was her emissary. Kali was recruited by the alpha, Deucalion alongside Ennis, to form a the Alpha Pack. She accepted the offer, killed all of her former pack to join, and was to do the same to Julia, but instead left her to die in peace. Kali became second in the pack as well as involved with Ennis. In Season 3, Kali, as part of the Alpha Pack, are in Beacon Hills, California to recruit alpha Derek Hale and then Scott McCall who has the potential to be a True Alpha. Kali participates with the alphas' plan to force Derek into joining them. They abduct his pack Erica Reyes, Boyd and his long-lost sister Cora Hale to lure him into a trap, with Kali killing a defiant Erica. The tension between the two packs leads to an all-out-battle, which results in Ennis being severely injured. Deucalion lies to Kali that Ennis had died from fighting Derek, and she swears revenge on Derek unless he joins in repentance. The alphas, including Kali redirect their attention to the Darach whom is committing human sacrifices in a move against them. She discovers the dark druid's identity: Jennifer Blake who is actually Julia, her old emissary having sworn revenge against Kali and the Alphas for attempting to kill her. Kali takes on Jennifer in combat but is outmatched and killed.
Kali is a formidable, strong-willed and proud woman with a sense of conviction, being the leader of her pack. She is unafraid to speak her mind but is blunt to the point of being arrogant and tactless.
"They killed one of ours!"
"One of yours. Why should I care about one of your pack?" - Kali to Ennis
These hot-headed characteristics of hers were most likely what Deucalion coveted so to bring Kali over to his new monstrous cause and recruit her for his new alpha pack. As a result Kali is a savage werewolf, being immensely bloodthirsty, ruthless and sadistic, has a dark sense of humor and displays no remorse for betraying and slaughtering her previous pack, drunk from subsuming their collective power. Like Deucalion, Kali is very smug and fanatical over her immense power and reputation as part of the alphas.
"Tell him what it's like, Kali, to kill one of your own."
Kali has a commanding presence, no sense of fear and is an effective leader, naturally being Deucalion's second. She is very loyal to Deucalion, follows his orders unquestionably even if she doesn't always agree with them as she scoffed at the idea of Scott and Derek joining the Alpha Pack, not considering them worthy of the privilege. At first though however, Kali's loyalty was transmutable: she only joined the pack to be with Ennis at first. Her previous loyalty to her emissary Julia reached far enough to simply leave Julia to die in peace after mauling her, going against Deucalion's order. Typical for a werewolf, Kali is extremely vengeful, blindly swearing revenge against Derek for her lover Ennis' death. Kali's ruthlessness and thirst for vengeance blinded her however that she paid no heed Marin Morrell's (truthful) claims that her leader was who actually killed Ennis, showing her poor sense of judgement which ultimately leading to her undoing. Kali never backed down from Jennifer (Julia) and her impending death.
"I ... I - I should have ... I SHOULD HAVE RIPPED YOUR HEAD OFF!!" - Kali's final words
Kali: "One of yours. Why should I care about one of your pack?"
A little while later, upon the declaration of war upon Packs by Gerard Argent, Kali was recruited by a spiralling, corrupt Deucalion to form the basis of the Alpha Pack. Kali accepted, partially to be with Ennis, hinting she and Ennis were having an affair. To join, Kali went on to murder her whole Pack to add all their individual power to hers.
When the Alpha Pack were at the height of their power, Kali rose and became Deucalion's right hand. At the time of Season 2, the Alphas arrived to Beacon Hills having taken notice of Derek Hale's rise to Alpha status. They captured Erica Reyes, Vernon Boyd and Cora Hale holding them captive at Beacon Hills First National Bank to set a trap for Derek. Erica attempted to fight back, but the malicious Alpha easily killed her.
"Count along with me, Isaac." (Holds up her shifted fingertips) "One. Two. Three."
Kali, along with the whole pack of alphas, infiltrates the high school and corner Braeden, who puts up a decent fight. Kali delivers Braeden the dealing blow. The subordinates back away as Deucalion confronts their target.
While on patrol with Deucalion and Ennis, Kali pauses for a short second by a supply closet. Allison Argent had infiltrated the bank and was hiding inside. Allison however, evades the malicious alpha's sense of smell by spilling ammonia to hide her scent.
Kali shrugs off her suspicion and walks on.
After Ennis restrains Cora, Kali challenges Derek. The younger alpha goes up against the malicious woman. Kali easily outmaneuvers and parries his strikes. She then rips off a rusty old pipe from up ahead, overpowers Derek and knocks him flat on his face, then impales him with the pipe through the chest, to subdue and torture him. Deucalion enters the loft.
Deucalion: "Sorry about this, Derek. I asked Kali to be gentle, but ... "
Kali: "This is me being gentle."
Deucalion scolds Derek for his assumption that they're there to kill him, then makes conversation. Kali has held the pipe in Derek long enough for him to bleed black ooze. Cora screams at Kali she's killing her brother. Kali waves a finger at the beta saying, "Not yet, little sister" in an endearing but dangerous tone. She advises her leader to get to the point of their presence.
Deucalion: "Tell him what it's like Kali, to kill one of your own.
Kali: "Hmm. Liberating.
Deucalion explains his proposition that if Derek kills one of his own, he'll absorb his beta's powers and abilities. The leader agrees with Kali that Derek looks like his mother.
With their intentions made, Kali removes the pipe from Derek's torso, and the alphas make their way out of the loft with Kali guiding her leader out.