You know, I have been thinking. Yes, I know how dangerous that is, but hey, life can get boring and this might make it interesting. Any who, for the kind Dr. Jekyll, if his 'Mr. Hyde side' were to be dormant for a while until he gains a level in summoner (Synthesist). the effect would be like he drinks a potion and changes into the eidalon. the mental stats would be the beast morpher stats due to the debilitating effect of the original concoction. Reading the description of both, I feel it best fits the concept. a level in one, then a level in the other.