Agni (Sanskrit: अग्नि) is the god of fire and the acceptor of sacrifices. The sacrifices made to Agni go to the deities because Agni is a messenger from and to the other gods. He is ever-young, because the fire is re-lit every day, and also immortal.
Agni is the first word of the first hymn of the Rigveda:
अग्नि॒म् ई॑ळे पुरो॒हि॑तं यज्ञ॒स्य॑ देव॒म् ऋत्वि॒ज॑म् । होता॑रं रत्नधा॒त॑मम् ॥
He is the supreme director of religious ceremonies and duties, and figures as messenger between mortals and gods. Vedic rituals all involve Agni, for example the elaborate Agnicayana, that is, the piling of the fire altar, the Agnihotra, viz., offering to Agni.
Lord Krishna describes Agni best among the eight Vasus;
रुद्राणां शंकरश्चास्मि वित्तेशो यक्षरक्षसाम्।
वसूनां पावकश्चास्मि मेरुः शिखरिणामहम्॥
Of all the Rudras I am Shankara[Lord Śiva], of the Yakṣas and Rākṣasas I am the Lord of wealth [Kuvera], of the Vasus I am fire [Agni], and of mountains I am Meru.
The Rigveda often says that Agni arises from water or dwells in the waters. He may have originally been the same as Apam Napat, who is also sometimes described as fire arising from water which in a natural explanation may have referred to flames from natural gas or oil seepages surfacing through water, or as the seven rays or bands of light of a rainbow. Other Rigvedic names, epithets or aspects of Agni include Matarishvan, Jatavedas, or Bharata.
Agni is a deva, second only to Indra in the power. He is Indra’s twin, and therefore a son of Dyaus Pita and Prthivi. However, he is also said to have two mothers (the two parts of the firedrill used to start the fire), and ten servant maids (the fingers of the man who is lighting the fire) or as the twice-born. He is one of the Guardians of the directions, representing the southeast.
Agni is the eldest son of Brahma. In Visnu Purana, Agni (Abhimani) the fire god is said to have sprung from the mouth of the Virat purusha, the Cosmic Man. His wife is Svaha. Abhimani had three sons of surpassing brilliancy: Pavaka, Pavamana, and Suchi, the personifications of the three fires that produced our earth and humanity. All these three names indicate purity. Abhimanin, his three sons, and their 45 sons constitute the mystic 49 fires of the Puranas and theosophy.