Lord Siva is the Lord of innumerable crores of Brahmandas or worlds. Isvara united with Maya gives rise to Brahma, Vishnu and Rudra out of Rajas, Sattva and Tamo Gunas respectively, under the command of Lord Siva. Brahma, Vishnu and Rudra are the trinities of the world.
There is no difference among the trinities, Brahma, Vishnu and Rudra. By the command of Mahesvara these three do the creative, preservative and destructive duties of the world. The work of all the three deities is done conjointly. They all have one view and one definite purpose in creating, preserving and destroying the visible universe of names and forms. He who regards the three deities as distinct and different, Siva Purana says, is undoubtedly a devil or evil spirit.
The Lord who is beyond the three Gunas, Mahesvara, has four aspects: Brahma, Kala, Rudra and Vishnu. Siva is the support for all the four. He is the substratum for Sakti also. Siva is distinct from the Rudra included in the trinities. Rudra is really one though according to the different functions He is considered to have eleven different forms.
The first face of Siva does Krida or play, the second does penance, the third destroys or dissolves the world, the fourth protects the people and the fifth, being knowledge, fully covers the entire universe by its power. He is Isana the creator and promoter of all beings, from within.
The first form of Siva is the enjoyer of Prakriti as Kshetrajna Purusha. The second is Tatpurusha resting in Sattva-guna, rooted in Bhogya-Prakriti, the Prakriti-enjoyed. The third is Ghora rooted in the eightfold Buddhi like Dharma, etc. The fourth is Vamadeva rooted in Ahankara and the fifth is Sadyojata, the presiding deity of the mind. The eight forms of Siva are Sarva, Bhava, Rudra, Ugra, Bhima, Pasupati, Isana and Mahadeva, rooted respectively in earth, water, fire, air, ether, Kshetrajna, sun and moon.