While there is a few slime levels, like Lichenous Lairs and the Royal Jelly levels, they don't really feel like they would be the final slime boss level. In Jelly King there's piles of slime in a few corners but it's mostly a castle that the slimes took over. So where did they come from? I want a level that's like a slimy cave type of thing, that's like completely caked with slime (maybe some of it can cause players to go a bit slower while walking through). Also a few giant slimes here and there would be neat, like jelly cubes who have absorbed the slime in the area and are giant like lichen colonies.

For slime mobs, I was thinking of something like from the game Amorphous+ ( http://kongregate.wikia.com/wiki/Amorphous%2B ). In this game, a guy with a big sword kills a bunch of slime monsters called glooples. There's a few interesting kinds of slimes among these that could do well in Spiral Knights. There's ones that leave some kind of sticky puddle behind that slows you down, there's one that shoots its babies onto the player and the things eventually grow into adults that can shoot more (this can probably be made into something like it grows new ones but they don't have the ability to make new babies but if you don't keep track of the real mother you'll have a rough time). There's one that hardens itself into a spiky ball that rolls at you, and its invincible while in spike form.

Here is the main idea though: the normal green slimes in the game are pretty harmless like lichens, but if they hit another green slime they have a chance to combine into a new form. It's not just a bigger form with spikes like the lichens though. The second form is like a bigger green thing that swallows the guy whole, the third form is some invincible metal ball with spiked edges that can harden itself when the player attacks and the only way to kill it is to stand still and let it make a metallic long spike that shoots towards you, which you can then dodge and attack it from behind (just like a trojan). The 4th form is some kind of black hole slime because there's so many slimes condensed inside of it that it becomes like that. There's also a toothy kind of slime that's just like the green slimes except its got teeth. When 2 of these combine, they can make a big blue thing that shoots out teeth like lichen colonies, but if these teeth hit green slimes, they transform into the toothy blue ones.

I'm not suggesting OOO rip off all of the ideas for monsters from this game or anything, just that adding more fusing kinds of slimes would be great because slimes are really the only kind of enemy that can do this, and I really like the combining aspect of lichens.