A Somayāga has an introductory or opening rite called Prāyaṇīyā and a closing rite called Udayanīyā.

These sacrifices belong to the iṣṭi type (see IṢṬI for details.)

The Prāyaṇīyā is performed after the dīkṣā (consecration of the sacrificer) day. Going out to fetch the soma creepers is the most important part of this rite. Offering of caru (porridge-like preparation) and ājya (ghee) to some deities is also done.

In the Udayanīyā iṣṭi, the concluding rite is performed in the fire of the shed called prācīnavaṁśa, erected with bamboos, with four oblations.