Most people agree this game is dying due to a lack of content. Everything is aesthetic updates. Even the new enemies are just lame versions of other existing monsters. There's a lot they could add, but I wanted to make a forum specifically for enemy ideas. With just a few new enemies and correct usage of them in combination with existing traps and monsters, this game could increase it's lifespan and playtime for months or possibly even years. I wanted to make a forum post to talk about this and even suggest actual monster concepts. My philosophy for enemy design is to have both the player's method of defeating them in mind (of course), but also how they work alongside other monsters.

Bacteria (Slime Family): "Infects" other enemies as they battle. If an infected monster dies, more bacteria will spawn from the body. This can change common focus orders. For example, normally a player may focus the Lumbers first. If a Lumber is infected though, a player may need to avoid the Lumber until the existing bacteria are dealt with so the bacteria population won't spread upon the Lumber dying and end up overwhelming the player. I'm not sure how the infection would be spread though. Maybe bacteria could leave an infection trail that infects anything that walks in it, or maybe they could prioritize nearby monsters instead of players (like how lichen respond to being near other lichen).

Gummy/Goopy (Slime Family): This enemy would have a nerfed version of the Giant Lichen Colony's dash attack with less damage, slightly less distance coverage, and longer delay between attacks. The difference here is it doesn't have specific targets. It dashes around randomly, each attack creating a circle of slime around it. For a Gummy, the circle would slow a knight's movement in it. For a Goopy, the knight will have much less friction in the circle. This will force players to choose between chasing the Gummy/Goopy so the environment won't be against them or focusing other monsters while battling with impaired movement. A lot of Spiral Knights's gameplay involves good positioning and kiting, so this enemy will easily work alongside most monsters. Gummies/Goopies won't accomplish much alone though.

Burglar (Fiend Family): Another Gremlin-series monster, and they're just as annoying and tricky as you'd expect. Burglars will pick up any items they find (Hearts, Loot, Potions, etc). Burglars that don't see any nearby loot will attack the player and force them to drop held heat and potions. After enough time, they will pull out a cell phone to signal they're leaving (calling transportation to bail out of the fight with their loot), and disappear after about 5 seconds. Players usually allow loot to sit around until the current fight they're in is over. The only thing players focus on during battle is hearts, and hearts are too important for survival to let go. Burglars will force players to race for drops so the Burglar can't run off with all their hard-earned loot. I'm not sure how the code for Spiral Knights looks, but I feel like this would be tough to program (mostly the part involving knocking heat and potions out of players), so this might be ignored simply due to technical difficulties/limitations.

These are a few ideas off the top of my head. If this post gets enough attention I'd love to make up more ideas with everyone.