Koranot was a boss from Castlevania IV. He was plainly put in there as a tech demo, a way to show off "fun with Mode 7 scaling". Of course, so was most of his level. His level, though is fun, for the most part, where-as Koranot is just a lame boss who is defeated quickly and without much fuss.
The Rock Monster, though, is a bad ass.
 
    

When evil spreads across the land, and darkness rises and the monsters roam. When the creatures of the night make beautiful music, and the things that go bump in the night go bump with greater enthusiasm. When the world is in peril and is in need of a hero...

These guys are, sadly, the best the world can hope for. These are the adventures of the heroes of CVRPG. They mean well, they try hard, and occasionally they do the impossible...

They actually do something heroic.