He is only truly interested in immortals and angels. He seems to have no concept of human morals but instead, has a sadistic sense of amusement and beauty. Eipos seems to have some mysterious interest in Rin, to the point that he hires mortal killers to target her.
SpoilerAs revealed in episode five, he is a hermaphrodite possessing qualities of both an angel and an immortal, which, according to him, makes him a "god". In episode three, he reveals that he is after Rin's time spore. Apparently, time spores contain the immortals' memories and Eipos enjoys consuming them. It is also revealed that he has the ability to instantly remove the spores from (thus, killing) both immortals and angels. Anyone else wishing to kill an immortal must do so by physically digging through their victims' flesh for the time spores. In episode six, Apos is revealed to be the child of Tajimamori, the previous Guardian of Yggdrasil, and the current Guardian himself. Guardians are supposed to switch every once in a (long) while, but Apos desires to become a permanent guardian by sacrificing Rin to Yggdrasil.