Gravis felt incredible nervousness and shock when the Red King unveiled his secret. This would change the whole dynamic between the white ape and him. The white ape was extremely powerful and had a high standing in the Empire, while Gravis was basically a weak nobody.
Yes, Gravis could be considered as a breeder for the Empress, but how many of those were there? Gravis had no idea, but he was sure that there were more breeders than level two Emperors in the Empire. Additionally, with the Empress' influence, she could get as many new mates as she wanted, but she couldn't get new level two Emperors as easily.
This meant that this situation had transformed into a situation where a way less valuable resource threatened a very valuable resource of the Empire. Just the danger alone that he posed might be enough reason to kill him. So, why had the Red King decided to tell them his secret now? Why was he putting his reward on the line like that?