Dreams and Nightmares is a pretty nifty mission but what it lacks is new enemies! This isn't necessarily bad for that one mission since it introduces a lot for one mission (as well as raises the difficulty substantially) but for future segments a few new swarm baddies would be pretty sweet, especially since doing so would help cover the current swarm's weak spots big time.

Another thing is that the enemies are kind of just reskins of existing enemies with very few tweaks. I wanna see some sweet black and red monsters that don't play by the rules, ya know?

Swarm Devilites

Step 1: Start with overtimer AI (no "normal" devilites or bosses)
Step 2: Give them the lichen dash attack, which they will use instead of just walking forwards
Step 3: Never flinches.
Step 4: Enjoys its job, more than you will ever know

Swarm Gorgos.. combined with toxigels
(Looks like a regular gorgo.. but with toxigel texture- also shows as slime/fiend when targeted)

Step 1: Strong against piercing and shadow, neutral to elemental and normal
Step 2: If knights are close, bites to attack like gorgos do
Step 3: If knights are not close, uses toxigel spin attack (uses ground pound animation)

Swarm Phantom.. combined with black kat
(Just looks like a phantom)

Step 1: Immortal as usual (would have to only spawn on special levels)
Step 2: Summons swarm zombies instead of doing its charge with gran faust/weird striker thing
Step 3: Is capable of doing the kat dash attack at random
Step 4: Touching the phantom deals strong curse to your knight

Swarm Scuttlebot

Step 1: Double the health of a normal scuttlebot, also larger model
Step 2: If the knight is up close, does the gremlin flamethrower attack (that spreads out) instead of bullets
Step 3: If the knight is far away, shoots a rocket puppy rocket
Step 4: Immune to freeze and fire

Swarm Stalkers

Step 1: Has the ability to cast all of gremlin mender's abilities
Step 2: Has slightly less health, but regenerates to full HP when invisible very quickly
Step 3: Razor blades drop to the ground as deconstructor bombs
Step 4: Immune to status effects, except curse

Swarm Howlitzer

Step 1: Shoots five swarm themed grave scarabs instead of bullets
Step 2: Skull spawns said grave scarabs as it travels towards the knight
Step 3: Passively spawns grave scarabs every time it takes damage
Step 4: Is larger and has more health

Swarm Totem

Step 1: Ressurects all swarm creatures, not just zombies
Step 2: Knight is cursed if inside of its circle of friendship (+10=max+max+med) curse resist to be immune
Step 3: Passively heals monsters, and gives them an attack buff

Swarm Griever

Step 1: Cannot be flinched, but is slower
Step 2: Always leaves trail of status effect cloud
Step 3: Attacks spawn 8 swarm bullets, in all directions

Swarm Toxilargo

Step 1: Passive health regeneration
Step 2: Has snarbolax's spike teleporting attack as its dash, goes to behind knight like a wolver would
Step 3: As it is attacked, random parts fly off (like from royal jelly fight) spawning glop drops

Swarm Lichen Colony

Step 1: When killed breaks into all of its smaller parts; i.e. normal swarm lichens which build it again at full hp
Step 2: Cannot do a normal attack, only the AoE spikes + random spin
Step 3: Dashes towards the source of bullets

Swarm Trojan

Step 1: Stomp attack does an AoE like tortodrone's does, but with shock
Step 2: Aggros knights that are charging a weapon first
Step 3: Much larger sword and range, no need for it to dash
Step 4: Attacks more frequently and with slightly faster animations

Swarm Rocket Puppy

Step 1: Shielded like a battle pod (Shield can be killed to get inside of it)
Step 2: Spawns Big Iron's tentacles from GitM when knights circle strafe it
Step 3: Shoots 3 rockets, then takes a while to reload

Swarm Kleptolisk (combined with deadnaut)
(Very large kleptolisk, displays as beast/undead)

Step 1: Resists shadow and elemental, neutral to normal, weak to piercing
Step 2: Very long tongue, which tracks the knight and steals vitapod then pills then other things
Step 3: Can become fully invisible and teleport (while invisible, so that it looks right) after a short while
Step 4: Resurrects swarm zombies
Step 5: AI resembles ghostmane stalker- find a good spot and try to snipe the knight, but with tongue

Design philosophy

The core shouldn't be a normal area and it shouldn't have normal rewards or normal difficulty.. it should offer players something to strive for, a reason to craft and grind for all of that fancy gear. None of this is just "fake difficulty" either- not just an increase in health and damage, but something truly terrifying.

All of the above exist in game somewhere as well- meaning that all of the mechanics are both easier to code and learned by players. The only big difference is the attack pattern + level of difficulty, which could be mitigated earlier on via level design, leading up to larger challenges that the game is sorely lacking at the moment.

Many of the above are designed to muck about with popular play styles- pepperbox is the only autogun that can counter swarm gorgos, and swarm trojans are going to be a lot harder to blitz through like you just don't care when they aggro you and stomp you at a distance... black kat set isn't nearly as useful when curse becomes commonplace... and brandish spam? Good luck with that against all of the minis and dividing enemies. You'll need much larger area of effect attacks for these.