Quote:
Ga Bu: Th-The...
The patriarch, he...he's...
<gulp> ...The patriarch is going to summon the Great Father again, and you have to stop him! Beat him, fight him, stop him!
Ga Bu: Ga Bu's parents said they didn't want it, along with many others! But the patriarch wouldn't listen. He was so angry─raging, fuming, angry!
Ga Bu: He said that if they didn't have iron in their hearts, they would serve as coke for the furnace. And then the guards took my parents and the others away, and I haven't seen any of them since...
Alphinaud: "Coke for the furnace“?
Alisaie: I did not want to believe it...but I have heard tales of foci fashioned from the bones of beastmen, which worshipers use in their rituals, hoping to summon more powerful incarnations of their gods.
So, Beast Tribes can do ritual sacrifices, and use the bones as foci to summon stronger Primals, but it definitely doesn't have to be from someone willing. Ga Bu's parents totally weren't on board with the summoning despite believing in the Great Father Titan, but they still got axed. While Alisaie does specify that the bones of the beastmen are being used, I wouldn't be surprised if a bone from any sacrificed race works, and it's simply the belief in the power of blood sacrifice that is leading to a stronger summoning.