अगस्त्येन तदा देवैः प्रार्थितेन महर्षिणा।
अनुभूय किल श्राद्धे भक्षितः स महासुरः॥
agastyena tadā devaiḥ prārthitena maha-rṣiṇā
anubhūya kila śrāddhe bhakṣitaḥ sa mahāsuraḥ
agastyena = Agastya; tadā = then; devaiḥ = by the devas; prārthitena = requested; mahā-ṛṣiṇā = the great sage; anubhūya kila = went through the formalities and; śrāddhe = during a śrāddha ceremony; bhakṣitaḥ = ate; saḥ = the; mahā-asuraḥ = great asura [Vātāpi].
Requested by the devas, the great sage Agastya then went through the formalities and ate the great asura [Vātāpi] during a śrāddha ceremony.1
1 It appears that anukūlaḥ appears in some manuscripts instead of anubhūya. But the latter is the reading of Śrī Govindarāja. Anukūlaḥ indicates that Vātāpi was eager to be eaten by Agastya (so that Ilvala can later kill the sage and eat him).
The formalities concerned the sage’s accepting [the invitation to participate in] the śrāddha ritual.