Kill King Gordok.
In Gordok society, their king is simply their strongest warrior. If anyone, ogre or otherwise, kills the current king, they are automatically hailed as the new one.
The new king receives tribute from any living guards, Stomper Kreeg, and Captain Kromcrush. Find and kill King Gordok while killing as few of their other leaders as possible, and not only will your reward be great, you will be able to use your power as king to halt the Gordok invasion without conflict!