The Rigvedic hymns are dedicated to various deities, chief of whom are Indra, a heroic god praised for having slain his enemy Vrtra; Agni, the sacrificial fire; and Soma, the sacred potion or the plant it is made from. Equally prominent gods are the Adityas or Asura gods Mitra-Varuna and Ushas (the dawn). Also invoked are Savitr, Vishnu, Rudra, Pushan, Brihaspati or Brahmanaspati, as well as deified natural phenomena such as Dyaus Pita (the shining sky, Father Heaven), Prithivi (the earth, Mother Earth), Surya (the sun god), Vayu or Vata (the wind), Apas (the waters), Parjanya (the thunder and rain), Vac (the word), many rivers (notably the Sapta Sindhu, and the Sarasvati River). The Adityas, Vasus, Rudras, Sadhyas, Ashvins, Maruts, Rbhus, and the Vishvadevas (all-gods) as well as the thirty-three gods are the groups of deities mentioned.