"I raised Lord Gernert myself. His house barely existed, and now it is gone." Prince Doran sighs. "Thistledown will go to Ser Donnel for his service."
Eutimio kneels before Prince Doran at [Town in Your Region]. "Ser Donnel tells me we have you to thank for our victory. He says you showed unmatched loyalty."
Ask what is to become of House Gernert now.
Say that you believe Lord Gernert was ill or mad.
Hesitantly wonder why Lord Gernert had to be killed once he'd been disarmed.
Subtly remind Prince Doran that it is [Your House] he owes his gratitude.
Prince Doran looks sad. "Ser Donnel believed I would want him executed. But I would rather have talked to him. Learned who was behind him."
Suggest that some of House Gernert's territories go to [Your House].