King Griffon knowledge is one of the hardest to get in the game. (I don’t know why) There is an easy way though!  There are two quests that require you to have King Griffon knowledge.  Those quests are: Revivify Knowledge & Co-Op Head of an Eagle, Body of a lion. Pro tip: Do these quests at the same time.  You can get them from an NPC in the middle pond area of Navarn Steppe. (See Map Below) In order to finish Revivify Knowledge quest, you have to obtain all the ecology knowledge in Steppe.  Press H (for Knowledge menu) Go to Ecology, Ecology of Kamasylvia and then the first one on top, Steppe of Kamasylvia.  You have to discover everything under Steppe.  Even if you have collected energy from Steppe ecology knowledge – in order, to finish the Revivify quest, nothing can be a ???.

Pro Tip:

Obtain all the knowledge under Steppe of Kamasylvia, leaving King Griffon for last. Once, you have everything but King Griffon, go to Milden. (He is located in the middle pond area) Milden will sell you King Griffon knowledge for 10 energy but only after you have the knowledge of everything else.