There are 1028 hymns in the Rigveda, most of them dedicated to specific deities. Indra, a heroic god, slayer of Vrtra and destroyer of the Vala, liberator of the cows and the rivers; Agni the sacrificial fire and messenger of the gods; and Soma the ritual drink dedicated to Indra are the most prominent deities. Invoked in groups are the Vishvedevas (the "all-gods"), the Maruts, violent storm gods in Indra's train and the Ashvins, the twin horsemen. Rivers play an important role, deified as goddesses, most prominently the Sapta Sindhu and the Sarasvati River.