Devapi (Sk.). A Sanskrit Sage of the race of Kuru, who, together with another Sage (Moru), is supposed to live throughout the four ages and until the coming of Maitreya Buddha, or Kalki (the last Avatar of Vishnu) ; who, like all the Saviours of the World in their last appearance, like Sosiosh of the Zoroastrians and the Rider of St. Johns Revelation, will appear seated on a White Horse. The two, Devapi and Moru, are supposed to live in a Himalayan retreat called Kalapa or Katapa. This is a Purânic allegory.
Source: H.P.Blavatsky - The Theosophical Glossary