Revelations: The Demon Slayer

If you go into battle and you fight a monster you have in your party (he doesn't have to be summoned) and start to talk to it. The monster will walk away.

To persuade Vaerial to join your party, first beat the game. Then return, traveling through the Nest of Zord, and talk to the monster on the former battleground.

Lich + Harpy =Kelpie L15

Mammoth + Kobold =Blue L12

Blue + Kobold = Kelpie L15

Kobold + Tanki = Kimalis L8

Kobold + Kelpie = Larun L13

Mammoth + Hecket = Kelpie L15

Blue + Kelpie = Kelpie L15

Mammoth + Hecket = Gayle L10

Blue + Hecket = Lich L1