When Gravis heard Aris speak, he felt like he was meeting someone completely new.
Aris had always had inner conflicts. Some parts of human psychology and beast psychology battled in his mind. One side told him that he should get into contact with others more and join a group, while another part of himself told him that he didn't need all that. He only needed power.
Gravis knew of all these inner conflicts, but when he saw Aris again, he felt that the conflicts had been resolved.
The Opposer had told Aris that he should go into a world where the tempering was organization-based, not species-based. In that world, humans and beasts joined the same powers, and they lived in relative harmony with each other. The enemies were not the ones that didn't look like them, but the ones belonging to other powers.
Apparently, living in such a world for such a long time had done a lot to shape Aris' personality.