A third and much less important group is that of the Vasus, mostly associated with Indra in the Rigveda, though in later Vedic texts Agni becomes their leader. They are a vague group, for they are not characterised, having neither individual names nor any definite number. The Brahmanas, however, mention eight of them. Finally, there are the Viçvedevas or All-gods, to whom some sixty hymns are addressed. It is a factitious sacrificial group meant to embrace the whole pantheon in order that none should be excluded in invocations intended to be addressed to all. Strange to say, the All-gods are sometimes conceived as a narrower group, which is invoked with others like the Vasus and Adityas. Besides the higher gods the Rigveda knows a number of mythical beings not regarded as possessing the divine nature to the full extent and from the beginning. The most important of these are the Ribhus who form a triad, and are addressed in eleven hymns. Characteristically deft-handed, they are often said to have acquired the rank of deities by their marvellous skill. Among the five great feats of dexterity whereby they became gods, the greatest--in which they appear as successful rivals of Tvashtri, the artificer god--consists in their having transformed his bowl, the drinking vessel of the gods, into four shining cups. This bowl perhaps represents the moon, the four cups being its phases. It has also been interpreted as the year with its division into seasons. The Ribhus are further said to have renewed the youth of their parents, by whom Heaven and Earth seem to have been meant. With this miraculous deed another myth told about them appears to be specially connected. They rested for twelve days in the house of the sun, Agohya ("who cannot be concealed"). This sojourn of the Ribhus in the house of the sun in all probability alludes to the winter solstice, the twelve days being the addition which was necessary to bring the lunar year of 354 into harmony with the solar year of nearly 366 days, and was intercalated before the days begin to grow perceptibly longer. On the whole, it seems likely that the Ribhus were originally terrestrial or aërial elves, whose dexterity gradually attracted to them various myths illustrative of marvellous skill.