Srimad-Bhagavatam: Canto 5 - Chapter 1 - Verse 3
यस्य ह वा इदं कालेनोपसञ्जिहीर्षतोऽमर्षविरचितरुचिरभ्रमद्भ्रुवोरन्तरेण साङ्कर्षणो नाम रुद्र एकादशव्यूहस्त्र्यक्षस्त्रिशिखं शूलमुत्तम्भयन्नुदतिष्ठत् ॥ ३ ॥
yasya ha vā idaṁ kālenopasañjihīrṣato ’marṣa-viracita-rucira-bhramad-bhruvor antareṇa sāṅkarṣaṇo nāma rudra ekādaśa-vyūhas try-akṣas tri-śikhaṁ śūlam uttambhayann udatiṣṭhat.
At the time of devastation, when Lord Anantadeva desires to destroy the entire creation, He becomes slightly angry. Then from between His two eyebrows appears three-eyed Rudra, carrying a trident. This Rudra, who is known as Sāṅkarṣaṇa, is the embodiment of the eleven Rudras, or incarnations of Lord Śiva. He appears in order to devastate the entire creation.
In each creation, the living entities are given a chance to close their business as conditioned souls. When they misuse this opportunity and do not go back home, back to Godhead, Lord Saṅkarṣaṇa becomes angry. The eleven Rudras, expansions of Lord Śiva, come out of Lord Saṅkarṣaṇa’s eyebrows due to His angry mood, and all of them together devastate the entire creation.