Read about the concept of Viparita Raja yog here
Phaladeepika describes about Vimala yog as below.
Definition
“If the lord of the 12th house occupies an evil house (6th, 8th) and is associated with or aspected by malefics, Vimala Yog is formed.”
Description
“The effects of a person’s birth in such a yog are that they spend much less than what they earn and save. They are good to everybody and their actions are identical with the thinking of others. They are very happy and independent and pursue respectable profession or occupation and are well known for their merits.”
Notes
The underlying concept of Viparita Raja Yog given in Uttara Kalamrita (Refer here) aligns with this Yog of Phaladeepika.
Where basics, of Dussthana lord placed in other (or same) Dussthana house gives favourable effects and end results, is kept under light.
Harsa Yog - Viparita Raja yog by 6th house and its lord
Sarala Yog - Viparita Raja yog by 8th house and its lord