Srimad-Bhagavatam: Canto 6 - Chapter 1 - Verse 17-18

Sanskrit:

सरूपासूत भूतस्य भार्या रुद्रांश्च कोटिश: ।रैवतोऽजो भवो भीमो वाम उग्रो वृषाकपि: ॥ १७ ॥अजैकपादहिर्ब्रध्नो बहुरूपो महानिति ।रुद्रस्य पार्षदाश्चान्ये घोरा: प्रेतविनायका: ॥ १८ ॥

ITRANS:

sarūpāsūta bhūtasyabhāryā rudrāṁś ca koṭiśaḥraivato ’jo bhavo bhīmovāma ugro vṛṣākapiḥ

Translation:

Sarūpā, the wife of Bhūta, gave birth to the ten million Rudras, of whom the eleven principle Rudras were Raivata, Aja, Bhava, Bhīma, Vāma, Ugra, Vṛṣākapi, Ajaikapāt, Ahirbradhna, Bahurūpa and Mahān. Their associates, the ghosts and goblins, who are very fearful, were born of the other wife of Bhūta.

Purport:

Śrīla Viśvanātha Cakravartī Ṭhākura comments that Bhūta had two wives. One of them, Sarūpā, gave birth to the eleven Rudras, and the other wife gave birth to the associates of the Rudras known as the ghosts and hobgoblins.