Sri Aurobindo translates Nilarudra Upanishad, First Part, Verses 1-3: “OM. Thee I beheld in thy descending down from the heavens to the earth, I saw Rudra, the Terrible, the azure-throated, the peacock-feathered, as he hurled. Fierce he came down from the sky, he stood facing me on the earth as its lord, — the people behold a mass of strength, azure-throated, scarlet-hued. This that cometh is he that destroyeth evil, Rudra the Terrible, born of the tree that dwelleth in the waters; let the globe of the storm winds come too, that destroyeth for thee all things of evil omen.”
The seer of the Upanishad has had a vision of the divine power of destruction which is part of the cycle of birth, life and death that functions to provide opportunity for growth, change and development. This force, when it manifests, is terrifying and overwhelming to the human being. We witness the reaction of Arjuna in the Bhagavad Gita when he is confronted with the vision of the Time-Spirit, the universal destroyer that is wiping away all of the obstacles to the next phase of evolution.
Sri Aurobindo has provided insight to these verses: “The speaker … records a vision of Rudra descending from the heavens to the earth. … the image in which he beheld the Divine Manifestation is described, Rudra, the God of might and wrath, the neck and throat blue, a peacock’s feather as a crest, in the act of hurling a shaft. … He descended fiercely, that is, with wrath in his face, gesture and motion and stood facing the seer … on the earth and over it, … in a way expressive of command or control. … The people see Rudra as a mass of brilliance, scarlet-ringed and crested with blue, the scarlet in Yoga denoting violent passion of anger or desire, the blue sraddha, bhakti, piety or religion. … Rudra, whom we know as the slayer of evil, comes. The Rajarshi describes him as born of the tree that is in the waters. … The asvattha is the Yogic emblem of the manifested world, as in the Gita, the tree of the two birds in the Shwetashwatara Upanishad, the single tree in the blue expanse of the Song of Liberation. The jala is the apah or waters from which the world rises. The Rishi then prays that the … mass of winds of which Rudra is lord and which in the tempest of their course blow away all calamity, such as pestilence, etc., may come with him.”
Sri Aurobindo, The Upanishads, Nilarudra Upanishad, pp.393-396