The Rig Veda is an ancient Indian sacred collection of Vedic Sanskrit hymns. It is counted among the four canonical sacred texts (sruti) of Hinduism known as the Vedas. The Rig Veda contains several mythological and poetical accounts of the origin of the world, hymns praising the gods, and ancient prayers for life, prosperity, etc. Some of its verses are still recited as Hindu prayers, at religious functions and other occasions, making it probably the world's oldest religious texts in continued use. 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. The hymns mention various further minor gods, persons, phenomena and items, and contain fragmentary references to possible historical events, notably the struggle between the early Vedic people (known as Vedic Aryans, a subgroup of the Indo-Aryans) and their enemies, the Dasa or Dasyu and their mythical prototypes, the Pani (the Bactrian Parna).