So, everyone here should know what the real goblin king looks like, right? The one that you see at the start thats like 'garrrr! We goblins love gold!' That is what he should look like.
Level 1-9 as he is normally, except for a wooden club with metal spikes coming out of it. Level 10-19 he gains a gem in his belly instead of a what is already there, he also gains a black helmet. Level 20+ he gains a dark metal club, (black) and he also gets a.... Whatever anyone thinks, what should he get at lvl 20???