Hardstone slime boss

[Note: im moving this here from the discord sugesstions, as those are now gone]

Boss: Grey slime covered in stones that need to be mined away before you can damage it. Its too heavy to jump, so it slides around, bouncing off the walls breaking them. When it bounces, it occasionally causes rocks to fall from the ceiling that turn in to more walls to bounce off of.

Small slimes: One stone on them, but they can be attacked normally. When hit they bounce around like the boss, but don't break walls.

Slime: Speed slime. Makes you move taster. good for paths, if you're fine with little bouncy guys spawning in your base.

Drops: Sometimes its stones can have ore in them, and drop when broken. also has a chance to give ore as basic loot. Also drops stone armor that negates a %portion of your current speed boost, but has high defense. A Heartstone pickaxe, or hand drill.

Location: New sub-biome, Hardstone caverns. Made of hardstone.
Magnesium chunks generate here.