Honestly, the Caves & Cliffs update is going to open so many doors for potential enemies! I even came up a couple of mobs themed off of the new biomes that'll be added in this update!
- Impaler: Spawning in Dripstone Caves, these weak enemies take the form of spider-like monsters with stalactites for protective shells. They like to cling themselves on the ceiling to blend in with the other stalactites before dropping down on uncareful travelers, dealing massive damage. However, in doing so they end up getting stuck in the ground for a few seconds, giving the player an opportunity to strike them down before they shoot a string of web up to the ceiling in order to pull themselves back up. They also tend to spawn in groups, too.
- Axolotl Mage: Spawning in Lush Caves, Axolotl Mages are unique and rare mobs that serve as friendly NPCs players can trade with, selling a handful of unique items and cosmetics found nowhere else in the world. Attacking an Axolotl Mage will cause it to teleport away, but not before casting a spell which turns the player into an axolotl for a few seconds! His most expensive item is the Axolotl Wand, which grants all tamed axolotls to float in the air as of they were underwater, allowing them to attack land enemies as well as aquatic ones.
- Raker: While the Warden rules over the Deep Dark, the Rakers reside within this biome as some of it's frightening denizens. Being nearly as tall as the player and armed with sharp scythes for hands, they will quietly stalk the player as the traverse through the Deep Dark and are able to crawl along the walls and upside down on the roof of the cave in pursuit of them. Although dealing with one of them can be manageable, a Raker at low health will have a chance of releasing a signal which attracts all other Rakers to it's current location, who will then attack the player if they don't escape quick enough. On death, Rakers will have a chance to drop their long claws, which can then be crafted into Climbing Hooks. Lastly, Raker naturally fear the Warden, and will flee whenever it is near.
I'm also thinking about potential mob ideas for flooded caves, too.