What is Vipreet Raja Yoga?
Vipreet (Viparita) Raja Yoga is the "reverse" Raja Yoga: it forms when the lord of a difficult house (6th, 8th or 12th) is placed in another difficult house. Two negatives cancel, giving a strong rise — often after struggle.
There are three forms: Harsha (6th lord in 6/8/12), Sarala (8th lord in 6/8/12) and Vimala (12th lord in 6/8/12).