Om Namo Bhagavate Vasudevaya!Beyond the Trimurti (i.e., Brahma, Vishnu, and Maheshwara), there is ParaBrahman (i.e., ParaVasudeva of the Vaishnavas, Nirguna Brahman of the Advaitins/Smartas, ParaShiva of the Shaivas, or Adi ParaShakti of the Shaktas).
ParaBrahman is the source of this universe and countless others.
janmādy asya yataḥ
Translation:
“(ParaBrahman) is He from Whom everything emanates.” - Brahma Sutras 1.1.2
ParaBrahman is the Lord of all beings and the source of devi-devatas’ names, roles, and powers.
yo naḥ pitā janitā yo vidhātā dhāmāni veda bhuvanāni viśvā
yo devānāṃ nāmadhā eka eva taṃ sampraśnam bhuvanā yanty anyā
Translation:
“He (i.e., ParaBrahman) who is our preserver, our parent, the creator, who knows our abodes and knows all beings, who is the name-giver and name-bearer of the devas – He is one; other beings come to Him to enquire." - Rig Veda 10.82.3
The devi-devatas represent the different aspects of ParaBrahman’s shakti, and they are part and parcel of ParaBrahman.
indram mitraṃ varuṇam agnim āhur atho divyaḥ sa suparṇo garutmān
ekaṃ sad viprā bahudhā vadanty agniṃ yamam mātariśvānam āhuḥ
Translation:
“They have styled Him (i.e., ParaBrahman), Surya, Indra, Mitra, Varuṇa, Agni, and He is the celestial, well-winged Garuda, for learned priests call one by many names as they speak of Agni, Yama, Mātariśvan.” - Rig Veda 1.164.46
ParaBrahman is also known as being ‘purna’ (‘complete’ or ‘full’ of transcendental essence/quality).
oṁ pūrṇam adaḥ pūrṇam idaṁ pūrṇāt pūrṇam udacyate pūrṇasya pūrṇam ādāya pūrṇam evāvaśiṣyate
Translation:
“The Personality of Godhead is perfect and complete, and because He is completely perfect, all emanations from Him, such as this phenomenal world, are perfectly equipped as complete wholes. Whatever is produced of the Complete Whole is also complete in itself. Because He is the Complete Whole, even though so many complete units emanate from Him, He remains the complete balance.” - Isha/Brihadaranyaka Upanishad Introductory Invocation
ParaBrahman cannot be known through our five bodily senses.
tadvā etadakśaraṃ gārgyadṛṣṭaṃ draṣṭṛ aśrutaṃ śrottṛ amataṃ mantṛ avijñātaṃ vijñātṛ nānyadato'sti draṣṭṛ nānyadato'sti śrotṛ nānyadato'sti mantṛ nānyadato'sti vijñātṛ etasminnu khalvakśare gārgyākāśa otaśca protaśceti
Translation:
“This Immutable, O Gārgī, is never seen but is the Witness; It is never heard, but is the Hearer; It is never thought but is the Thinker; It is never known, but is the Knower. There is no other witness but This, no other hearer but This, no other thinker but This, no other knower but This. By this Immutable, O Gārgī, is the space pervaded.” - Brihadaranyaka Upanishad 3.8.11
ParaBrahman can only be known from the authorities of scripture.
śāstra-yonitvāt
Translation:
“Because He (i.e., ParaBrahman) may only be known by the Vedic scriptures.” - Brahma Sutras 1.1.3
The nature of ParaBrahman is nirguna (i.e., devoid of and beyond material qualities) and saguna (i.e., of transcendental quality).
tam īśvarāṇāṃ paramaṃ maheśvaraṃ taṃ devatānāṃ paramaṃ ca daivataṃ
patiṃ patīnāṃ paramaṃ parastād vidāma devaṃ bhuvaneśam īḍyam
na tasya kāryaṃ karaṇaṃ ca vidyate na tatsamaś cābhyadhikaś ca dṛśyate
parāsya śaktir vividhaiva śrūyate svābhāvikī jñānabalakriyā ca
na tasya kaścit patir asti loke na ceśitā naiva ca tasya liṅgaṃ
sa kāraṇaṃ karaṇādhipādhipo na cāsya kaścij janitā na cādhipaḥ
Translation:
“We know Him who is the Supreme Lord of lords, the Supreme Deity of deities, the Ruler of rulers; who is higher than the imperishable prakriti and is the self-luminous, adorable Lord of the world. He is without a body or organs; none like unto Him is seen, or better than He. The Vedas speak of His exalted power, which is innate and capable of producing diverse effects, and also of His omniscience and might. He has no master in the world, no ruler, nor is there even a sign of Him by which He can be inferred. He is the cause, the Lord of the lord of the organs; and He is without progenitor or controller.” - Svetasvatara Upanishad 6.7–9
ParaBrahman is transpersonal (i.e., beyond personality) with both impersonal (i.e., Brahman) and personal aspects (i.e., Bhagavan), as well as an immanent aspect (i.e., Paramatma).
vadanti tat tattva-vidas tattvaṁ yaj jñānam advayam brahmeti paramātmeti bhagavān iti śabdyate
Translation:
“Learned transcendentalists who know the Absolute Truth call this nondual substance Brahman, Paramātmā or Bhagavān.” - Srimad Bhagavatam 1.2.11
The ways of ParaBrahman are seemingly contradictory.
tad ejati tan naijati tad dūre tad v antike tad antar asya sarvasya tad u sarvasyāsya bāhyataḥ
Translation:
“The Supreme Lord walks and does not walk. He is far away, but He is very near as well. He is within everything, and yet He is outside of everything.” - Isha Upanishad 5
ParaBrahman is represented by the sound/mantra/symbol ‘Om’.
sarve vedā yatpadamāmananti tapām̐si sarvāṇi ca yadvadanti yadicchanto brahmacaryaṃ caranti tatte padm̐ saṃgraheṇa bravīmyomityetat etaddhyevākśaraṃ brahma etaddhyevākśaraṃ param etaddhyevākśaraṃ jñātvā yo yadicchati tasya tat
Translation:
“The goal which all the Vedas uniformly extol, which all acts of tapas speak of, and wishing for which men lead the life of a Brahmacharin, that goal I tell you briefly — It is this — Om. This word is, indeed, Brahman, this word is, in deed, the highest; whoso knows this word obtains, indeed, whatever he wishes for.” - Katha Upanishad 1.2.15–16
Hare Krishna