Lord Shiva is one of the trinity of gods in Hinduism. Considered the manifestation of the Apara Brahman (Formless Supreme Source of the Universe) in a form to be enjoyed and worshipped by the devotees, Shiva is considered the destroyer or annihilator or the final destination of the entire gamut of creation. The other two among the trinity namely Brahma and Vishnu are said to be the creator and the protector respectively.
The role of destruction attributed to Lord Shiva has several shades of meaning to be understood and assimilated. The first and the obvious meaning is the role of dissolving or destroying the entire creation during the Pralaya (Great Floods) to be merged back to the source from which all this emanated. In this sense, Shiva is the massive destructive force that absorbs everything into itself at the end of dissolution.
This would mean that the destination (Shiva) exists after the universe dissolves into its source of origin. Therefore Shiva is the Supreme Principle or the Eternal Truth described as Sat, Chit and Ananda meaning Truth, Consciousness and Bliss. Hence the order of creation is as follows. From Shiva emerged Vishnu, from Vishnu’s naval emerged Brahma and the creation started. Upon dissolution, Brahma along with the cosmos merges back into Vishnu and Vishnu merges back into Shiva thus completing one cycle of creation.
The term destroyer is also used in another sense namely the destroyer of ignorance or Maya. Shiva is the embodiment of Supreme Knowledge. He is the fountain head from where all the gods, sages and saints imbibe their wisdom to be passed on to the last member in the created universe. Here the destroyer means the one who destroys ignorance lights up knowledge. While Maya is the cause of creation, removal of Maya means destruction.
Shiva is shown in a meditative form enjoying absolute silence, stillness and unadulterated bliss. He is in the constant state of changelessness. Therefore He stands as the visible symbol eternity that cannot be changed, mutated or destroyed. In this sense, Shiva is the final state of everything that is created. In this sense, He is the destroyer who can never be destroyed.