This Star Emblem belongs to Buwaro Elexion. It was given to him by his adoptive father, Darius Elexion, in order to suppress Buwaro's primal berserker state and enable him to think clearly. If it is removed from Buwaro's person then he will revert to that nightmarish state until the pendant is put back on him or he dies.
Buwaro's Emblem is possibly unique as Darius removed the Holy Protection Spell that prevents non-Angels from using it. Angels wear them to increase their magic power, Buwaro's magic skills are quite poor so it isn't clear if it helps him with that or not.