At some point, he began to use his magic in order to control a sect of the Hive. He is able to control and twist the nature of lesser creatures to his will, and has been forcing this clan of Hive to serve him and his whims. May have even changed his form to seem more Hive-like. That is why the greater Hive beings associated with him (Crota, Omnigul, Ir Yut, etc) are so much more powerful than all of the other Hive in their swarms. He has given them power and thus changed them into something more than just Hive. Crota even gained enough power to become like a god, like a son, to Oryx. I could even see the last remaining Ahamkara hiding in plain sight like this elsewhere. Maybe Osiris is one of them. Maybe one of the Nine is in Ahamkara. Who knows?