The building of this altar is spread over a whole year, during which period the sacrificer has to carry about the sacrificial fire in an earthen pan for at least some time each day, until it is finally deposited on the completed altar to serve as the offering-fire for the Soma oblations.
This is what may conveniently be called the Prajapati theory, by which the "Lord of Creatures," the efficient cause of the universe, is identified with both the sacrifice;(yajna) and the sacrificer (yajamana).
An important collateral identification is that of Prajapati (and the sacrificer) with Agni, the god of fire, embodied not only in the offering-fire, but also in the sacred Soma-altar, the technical name of which is agni.
Similarly the sacrificer, as the human representative of the Lord of Creatures, is identified with Soma (as the supreme oblation), with Time, and finally with Death: by the sacrificer thus becoming Death himself, the fell god ceases to have power over him and he is assured of everlasting life.
And now we get the Supreme Lord in his last aspect; nay, his one true and real aspect, in which the sacrificer, on shuffling off this mortal coil, will himself come to share - that of pure intellectuality, pure spirituality - he is Mind: such is the ultimate source of being, the one Self, the Purusha, the Brahman.