The Sadāśiva chakra is composed of five chakras: Tatpuruṣa, Aghōra, Vāmadēva, Sadyōjāta, and īśāna.
Here the word chakra refers to yantra (maṇḍala), mūrti, and mantra, and hence a sort of saṅkētatraya for the five-fold diversity is seen in all these aspects. The mantra chakra originates from the mantra śuddha praṇava with its five components: a, u, ma, bindu, and nāda. These represent Tatpuruṣādi mūrtis. From the praṇava arises the five-lettered mahāmantra popularly known as śuddha pañcākṣarī mantra. The five letters of this mantra represent the five mūrtis (Tatpuruṣādayaḥ). From each of the letters of this mantra originate five pañcākṣarī mantras known as the mukhya pañcākṣaras:
īśāna, Sadyōjāta, Vāmadēva, Aghōra, and Tatpuruṣa pañcākṣaras.
From each letter of these mantras, five pañcākṣaras originate i.e. from every mukhya pañcākṣara mantra, twenty-five pañcākṣara mantras emanate:
Tatpuruṣa
Ananta, Aghōra, Saumya, Rudra, Hamsa, ātma, ājñā, Madana, Māyā, Mantra, Amr̥ta, Prapañca, Sārasvata, Skanda, Mūla, Mahat, Kailāsa, Mr̥tyuñjaya, Lakṣmī, Kṣipra, ānanda, Anaṅga, śāmbhava, Jvālā, and Sarvasiddhi pañcākṣaras.
Aghōra
Vidvēṣa, Savya, Satya, Brahma, Viśva, Varuṇa, Samudraśōṣaṇa, Garuḍa, Gaja, Bhramara, Saṁgrāma, Yōginī, Gaṇa, śārabha, Gandharva, Vidyādhara, Sandhāna, Sr̥ṣṭi, Samhāra, Chitra, Vyaṣṭi, Samaṣṭi, Vaiśvānara, Parjanya, and Yakṣa pañcākṣaras.
Vāmadēva
Stambhana, Prajñā, Stōtra, Vimāna, Mānasa, Dhēnu, Purūhūta, Icchā, Laghu, Saura, Baindava, Sañcāra, ālōka, Vijñāna, Khēcara, Pañcasadākhya, Manōvēga, śubha, Gīrvāṇa, Svarga, Viṣa, Sundara, Ghaṇṭā, Sañjīvana, and ākhaṇḍala pañcākśaras.
Sadyōjāta
Bhēdana, Prājāpatya, Mahābala, Nirvāṇa, Nayana, Giri, Viṣṇu, Uccaiśrava, Mandākinī, Samvarta, Aghamarṣaṇa, Anāhata, Mēgha, Pavana, Siddhi, Yajña, Pūjā, Parimala, Sasya, Dik, Jihvā, Karṇa, Chit, Jñāna, and Sambhōga pañcākṣaras.
īśāna
Prāsāda, Prāsādagōcara, Prāsādasundara, Prāsādaśēkhara, Prāsādasaura, Prāsādabandhana, Prāsādabhujanga, Prāsādakamala, Prāsādacandra, Prāsādavidyādhara, Prāsādavijñāna, Prāsādacintāmaṇi, Prāsādadīpaka, Prāsādavidyātanu, Prāsādakamalānanda, Prāsādakavaca, Prāsādaratnākara, Prāsādakaustubha, Prāsādalakṣaṇa, Prāsādakuṇḍalī, Prāsādacūḍāmaṇi, Prāsādapāramēśvarīya, Prāsādaśaiva, Prāsādaśakti, and Mahāprāsāda pañcakśara mantras.
Each of the 125 pañcākṣara mantras confers different siddhis. For example, the siddhi associated with Prāsādakamalānanda is bhuvanādhva darśana, Prāsādacintāmaṇi is sōmamaṇḍala darśana, Karṇa pañcākṣara is karṇa siddhi, Nayana pañcākśara is dūradarśana siddhi, Khēcara pañcākṣara is ākāśagamana siddhi and so on.
Thus, this results in a total of 125 + 5 + 1 = 131 mantras (excluding praṇava) which again amounts to the number 5 (1+3+1). As these 131 mantras with praṇava acting as mantra vīrya for each of them are hidden within the Prāsāda, this great mantra of Sadāśiva is termed as the seed or bīja of every mantra belonging to śaivāmnāya. Hence, the ūrdhvāmnāya Tantra describes the siddhi of prāsāda as equivalent to the siddhi of the entire gamut of śaiva mantras. When we speak of prāsāda, the reference here is to śuddha prāsāda (of śaivāmnāya) but due to its presence within Parāprāsāda and Prāsādaparā, this would hold good even in the case of these mantras belonging to śāmbhavāmnāya. Hence it is said regarding the Mahāprāsāda mantra:
तमाचार्यं विजानीहि द्वादशार्णप्रदं शिवे ।
गुरुः प्रासाददाता स्यादुपाध्यायः प्रकीर्तितः ॥
षडक्षरी प्रदाता तु साङ्गोपाङ्गं महामनुम् ।
ददन् स परमाचार्यो सैव देशिकराडिति ॥
इमं मनुं नरो यस्तु सकृज्जपति भूतले ।
गुरुं सन्तोष्य यत्नेन पूजयित्वा स्वकर्धनैः ॥
स एव मुक्तिसाम्राज्यपदवीभाङ् न संशयः ।
शैवं षडक्षरीमाहुः पूर्वाङ्गं श्रुतयः शिवे ॥
द्वादशर्णं तथा प्राहुरुत्तराङ्गं शिवागमाः ।
प्रासादमाहुर्हृदयं सर्वाम्नायगताः शिवे ॥
विद्याविहीनोपि धनैर्विहीनः पुत्रैर्विहीनोपि यशसा विहीनः ।
विद्यामिमां कामितकल्पवल्लीं साङ्गां ब्रुवन् पातकसङ्घमुक्तः ॥
शिवोपि चाहं स्वमुखैर्युतः सन् विधिश्च वा विष्णुरथामरा वा ।
माहात्म्यमस्याः प्रभवन्ति नात्र किं वक्तुमन्ये प्रभवन्ति मूढाः ॥
The anuṣṭhāna of Sadāśiva chakra and Pañcākṣara prāsāda raśmi nyāsa are performed during Pradōṣa and importantly on the last prahara of Mahāśivarātra. The observance of Sadāśiva chakra in its aspects of mantra, mūrti, and maṇḍala grants pañcānga śuddhi without which inner alchemy has been declared as unattainable by the Rasa siddhas.