The second mantra of Māṇḍūkya Upaniṣad reads: sarvaṁ hy etad brahma | ayam ātmā brahma | so ’yam ātmā catuṣpāt || “All this is verily Brahman.  This Ātman is Brahman.  This Ātman has four quarters.”  What is Reality? It depends on your point of view, your state of consciousness.The "four quarters" are four states of consciousness: jagrat, svapna, suṣupti and turīya.  Śiva also looks different from different states of consciousness.  
Download Māṇḍūkya Upaniṣad: https://archive.org/download/mandukyaupanishadswaminikhilanandar.k.mutt1936_202003_845_e/Mandukya%20Upanishad%20%20Swami%20Nikhilananda%20R.K.%20Mutt%201936_text.pdf