Gaj Kesari Yoga is one of the praised yogas by scholars, and it should be because it is not a normal yoga.
It can be very positive as well as negative as hell. Yes, it is know to be a positive yoga only but it is not.
Though this yoga is formed by the great benefic Jupiter and Moon.
Formation of this Yoga: Sh. Parashara ji says,
Means: Jupiter should be in kendra to moon or ascendant and well aspected by benefic planet. It should not be in sign of debilitation, enemy or combust.
What I observed: If Jupiter is in kendra from both moon and ascendant and in 10th house from moon, is the highest level of this auspicious yoga, even if there is malefic relation some results are visible. Also, Jupiter in kendra from lagna is not powerful, from moon is important. Even if any one of them is debilitated but well aspected then also results are good. But debilitated planet should be favorable (having good lordship) to lagna. Jupiter has greater importance here.
Positive features: Prosperous, intelligent, spiritual, liked by mass, having sterling qualities and honest.
Negative features: Dumb, poverty, all type of problems, disputes, lack wisdom etc.
Now, why negative?
If the Jupiter is functional malefic from lagna, in debilitation sign, weak, combust, retrograde and aspected by malefics then this yoga becomes very negative. Same applies with moon but moon is secondary in this yoga.
Also see D-9, D-12, D-3, D-16 and D-60 chart for deep meaning of any yoga in horoscope. If planets in trouble in these divisional then results are reduced for that divisional chart.
Lastly, Gaj means elephant and Kesari is Lion. So, it has both Sattvik and Rajsik qualities. But it’s manifestation depend on other association of horoscope.