Here are my boss monster designs, i stuck with the typical dragon for one, the dragon design itself is pretty standard but it was an interesting sketch. I didn't bother with silhouettes for these i just sketched out the designs and worked them up. I think the dragon turned out pretty well.
The other monster is called Sawtooth and takes the place of Baron Nashor from League of legends. It is a burrowing monster that inhabits the moon where the arena is held. it's an odd character but it accomplishes the dangerous large monster vibe.