Ok. So...
I state what I said before, that I loved your idea. So...this idea will be similar, if its okay. This also may explain a few things with the story.
Once there was a powerful being by the name of Xylem (Snivy species). For "some reason" (not decided yet) he was forced to become four disciples. Thus the four Snivy. Xylem is a mythical being who can transport to "other worlds", or the heavens. He represents four destructive types: Fire, Dragon, Poison, and Ice. Each disciple has an alter ego/fusion related to one type. (Ex: Xivy is Fire)
If one disciple kills another, the killer gains that disciple's powers. If all four were to form as one, Xylem would be reborn. Xylem's subconscious rests in one specific disciple. Icin, who wants Xylem reborn to fullfill his goals. Thus he wants to murder the three others. Only Icin knows about the past regarding Xylem, not the other three.
