Chapter 23 of 42 · Shata Rudra Samhita · Overall chapter 252 of 464
Vrisha Avatara
Shiva assumes the form of a bull, Vrisha, and kills Vishnu's unruly sons by the amrita-born women outright; when Vishnu himself attacks in response, the two fight until Vishnu, exhausted and ashamed, recognises his own lord and submits - surrendering his old Sudarshana chakra, receiving an even more powerful replacement from Shiva, and being barred, along with the other gods, from re-entering Patala's pleasures by a permanent curse.
Nandishvara said
The Pinaka-wielder roared in the form of Vrishabha, entered the hole and roared in a terrible voice. His roars brought down cities and towns and all the cities' residents trembled. Vrisha rushed at Hari's sons, who stood ready with their bows. Those strong, valiant ones, confounded by Shiva's maya, were enraged, and the brave ones roared and rushed at Shankara. Seeing Hari's sons coming, he, in bull form, grew angry and shattered Vishnu's sons with his horns and hooves. All their limbs were mangled by Rudra and he swiftly destroyed them, and they lost their senses and their lives. When his sons were killed, the revered Vishnu, supreme among the strong, came out and quickly rushed at Hara. He saw Rudra wandering in bull form after killing his sons. Keshava struck him with divine arrows and weapons. Mahadeva in the form of Vrisha was angry, proud of his strength, and, immobile as a mountain, took Vishnu's weapons. Maheshvara as the bull, filled with great wrath, gave a loud terrible roar that made the three worlds tremble and struck Vishnu powerfully with horns and hooves. Vishnu was overwhelmed by rage too and in his folly did not know himself, but he grew slack and his limbs pained. Hari could not bear those blows and was confounded. He lost his pride and regained the senses he had lost, and came to know that Paramesha was wandering as Vrisha.
Realising it was Gourisha in the form of Vrisha, he calmed down, lowered his shoulders, joined his hands and spoke in a deep voice: lord of the gods, Mahadeva, ocean of compassion, I am foolish and deluded by your maya and have fought against you, my own lord. Please pity me and forgive this offence. Bhagavan, kind to devotees, heard Hari's miserable words and answered Vishnu: how did you not know me, wise one? You forgot all your knowledge and fought me. Do you not know your own self and that your valour depends on me? You should not have engaged in this union. Give up this wicked conduct. How can one with knowledge fall under Kama's sway and become addicted to pleasure with women? This is not worthy of you; remember that you are the one who saves the universe. Lovingly he heard Shambhu's words, which gave understanding, and, ashamed, Vishnu said he would accept them, he was one who carried out Shiva's commands, and his discus was here and he would take it and return to his own world. Mahesha Hara heard and, in bull form, told Hari again he should not delay but go quickly, and, by his command, let his discus stay in this world. He would give him a discus he would think even more terrible, greater than the sun at the time of destruction. Saying so, Hara made a divine, supreme discus, blazing like the fire of destruction, able to destroy all the wicked, and gave Vishnu this discus, terrible and as bright as ten thousand suns. The great-souled protector of all the immortals and lords of sages got another Sudarshana discus, supremely radiant. Vishnu, wisest of the intelligent, told the gods there to listen and act quickly on his words, which would benefit them: there were divine, beautiful, young women in Patala, and whoever wished could go and take pleasure with them. Hearing Keshava, the brave heaven-dwellers wished to enter Patala with Vishnu.
Knowing what they were thinking, Bhagavan Hara went there. Angry, he laid a terrible curse on eight species of gods: except for a calm sage and danavas born as his portion, anyone who entered this place would at once be destroyed. Hearing those terrible words, which served the welfare of humans, and repulsed by Rudra, the gods returned to their own abodes. Vishnu, who had become excessively addicted to women, was chastised by Shiva. He returned to his own world and the universe regained its natural state. Shankara, kind to devotees, in the form of Vrisheshvara did the gods' work and returned to his own excellent mountain. Thus the Vrisheshvara avatara is told: Sharva took away Vishnu's delusion and brought happiness to the three worlds. This sacred account removes great obstacles set by enemies and gives the virtuous heaven, fame, long life, enjoyment and liberation. A person who controls himself and listens devotedly, or has it heard, enjoys all he wishes and finally gains liberation, and the same is true of an intelligent man who reads it.
Retold in our own words from Bibek Debroy's English translation of the Shiva Purana (Penguin Classics). Names, numbers and the order of events follow the source.