KALKI: 2898 AD. The future is ours 

In 3102 BC, following the Kurukshetra War, Ashwatthama attempts to kill Uttarā's unborn child. For committing the act, Krishna, the 8th reincarnation of Vishnu, curses him to roam the earth as an immortal and witness humanity's misery as a result of societal and moral deterioration during the Kali Yuga. His divine gem is also taken from his forehead, and his redemption is destined to occur only by protecting the mother of Kalki, Vishnu's 10th and final reincarnation, towards the end of the Kali Yuga.^[c]

In 2898 AD, 6000 years after the events of the Kurukshetra War, Kasi stands as the last known city in a post-apocalyptic world dominated by Supreme Yaskin, a 200-year-old totalitarian god king. Yaskin rules from the 'Complex', an inverted-pyramid megastructure that floats above the city. His authority is enforced by Commander Manas, Counsellor Bani, and an army of soldiers who guard against threats, particularly rebels from the hidden city of Shambhala,^[d] who believe in the prophesied arrival of Kalki. In this dystopian society, fertile female refugees in Kasi are forcibly taken to the Complex for Project K, an experiment aimed at producing a secretive serum for Yaskin through artificially inseminated foetuses. However, the serum does not become potent until after a 150-day gestation period, and none of the subjects have survived for that long, nor do they survive the extraction procedure.

Raia, a young girl disguised as a boy, narrowly escapes conscription into Project K with the help of Shambhalan rebels. Raia finds refuge in a cave where she encounters Ashwatthama. She unknowingly brings him his divine gem, which had inadvertently come into her possession during her escape. After placing the gem in his forehead, Ashwatthama becomes aware that a woman is pregnant with Kalki. Together, the duo set out to find her.

Meanwhile, at the Complex, SUM-80, a Project K subject hiding her 150-day pregnancy, is outed and forced to undergo the extraction procedure. Manas extracts a single drop of serum from her foetus before she is rescued by Shambhalan rebels, who rename her Sumathi. En route to Shambhala their transport is ambushed by bounty hunters and raiders, but they fend them off. Bhairava, a bounty hunter, remains in pursuit with his AI supercar, Bujji.

Soldiers from the Complex corner Sumathi and the rebels. Ashwatthama and Bhairava arrive and defeat the soldiers, before fighting each other for the custody of Sumathi, who is revealed to be the mother of Kalki. Despite Bhairava's best efforts, Ashwatthama subdues him and the party reaches Shambhala, where the tree of life blooms in Kalki's presence. Ashwatthama reveals to Raia that his walking stick is a dormant weapon, the Vijaya Dhanush, that belonged to his friend Karna, a warrior from the Kurukshetra War. Meanwhile, Bhairava makes a deal with Manas to capture Sumathi in exchange for entry into the Complex.

Bhairava tricks a rebel into taking him to Shambala, then disguises himself as Ashwatthama and convinces Sumathi to flee Shambhala with him, but is intercepted by the real Ashwatthama. As they fight, Manas and his soldiers reach Shambhala and breach its defences. Shambhala's leader, Mariam, attempts to protect Sumathi, but she is killed by Manas as his soldiers overwhelm the Shambhalan rebels. Ashwatthama and Bhairava help save Sumathi, but afterwards Ashwatthama knocks Bhairava unconscious before Manas captures and restrains him. Ashwatthama's walking stick and a leaf from the tree of life subsequently falls into the unconscious Bhairava's hand, which reawakens both the weapon and Bhairava, revealing him to be a reincarnation of Karna. Empowered by Karna's bow, in a trance-like state Bhairava effortlessly defeats the invading soldiers and kills Manas. Snapped out of the trance by Bujji, Bhairava returns to his former self and takes Sumathi away, as Ashwatthama looks on.

In a mid-credits scene, Yaskin uses the drop of serum extracted from Sumathi's foetus on himself, partially gaining the power of the unborn Kalki and becoming a youthful superhuman with four magical limbs. He picks up Arjuna's bow, Gandiva, and pledges to personally capture Sumathi and her child to reshape the world.