The remaining tribes of the Heights were given two options.
Either join Kael, get food, a roof and security, in exchange for promising peace, or they could remain in their tribe, hunt for food themselves, worry about a roof and safety themselves and the only thing Kael would promise them would be that his Alliance won't be the first to attack them.
And…
As much as these people hated Kael, they were only the elderly and the children, they still had roofs, that wasn't the problem but safety was.
After all, it wasn't just tribes that attacked each other in the Heights, Beasts of the Wild often attacked as well and every Tribe needed a way to protect themselves from them.
The elderly and the children couldn't survive such attacks, so the only choice they had was to join Kael and that made them feel bitter. To join the same people who killed their kin, they found it hateful.
