Belias: Ashe
Mateus: Ashe
Adrammelech: Ashe
Zalera: Ashe
Shemhazai: Ashe
Cuchulainn: Ashe
Exodus: Ashe
Hashmal: Ashe
Zeromus: Ashe
Famfrit: Ashe
Chaos: Ashe
Ultima: Ashe
Zodiark: Ashe

I assigned all of the Espers to Ashe only because I felt that she was the only character in the game that would logically have a connection or pact with otherworldly creatures.