I played this mod for a while and I must say this mod is just great! I especially like the granite enemies. Those flying things are most original enemies I've ever seen. I'm really keen on idea of an NPC dropping out of the boss. Although, it seems to go more with King Slime, it also really fits in with the Queen Jellyfish (oh, she flies in midair!) and the Diver. The Creator if this mod is a genius!
Also, it seems like the Granite Armor is just OP. Before, lava was something really dangerous, something the player has to avoid. With Granite Armor lava is the safest place in the world, nothing can catch you, you cannot even drown! Wow! It also gives a TON of defense, and it's easy to get comparing it to like Magma Armor or Molten one. I suggest to give it a Lava Charm effect rather the whole fire immunity. Idk, how is it on Expert Mode but on Normal Mode, almost nothing can kill me.