Promote his lieutenant
From Create Your Own Story
Your lieutenant is happy to take the goblin chief's place. He is very fearful of you and is unlikely to have any more gladiator matches.
What now?
You need more power.
The princess you have prisoner could give you leverage over her Kingdom.
If you aren't so confident about this, you took make the foreign merchants that travel to the kingdom pay you a toll.
Alternatively, your goblins can take a nearby village, gaining you more followers.
