well 1.17 will add a lot of new cave biomes like the dripstone or lush caves. but here is an idea for a new one. The slime cave[/p]
generation - when a slime chunk is found then it has a 1/25 chance to make/change a surrounding cave into a slime cave.[/p]
mobs - this would spawn slimes all the time[/p]
appearance - it would have a very mossy look with slime blocks littering the walls and ceiling.[/p]
finally the boss - each cave would spawn a non-despawnable giant slime mini boss guarding the loot. well you might think can't you just go around the slime, get the loot and get out? no. this mob would have the loot inside of it's slime body and to get the loot you have to kill it. I don't know what it could drop but leave any ideas in the comments.[/p]
Giant Slime boss in a new slime cave biome