"Swarm Arena": an endless zone for postgame players

So everyone's still asking for a better way to grind radiants, right?
I suggest a "swarm arena" that acts as an endless survival zone.
Basically how it'd work is that you play through the arcade to get to the core (yes, this is arcade specific) and then after completing DaN (maybe, not sure about this) you can descend into the core and fight endless arenas (the mission kind, where you have to do all three).
Obviously, you'd fight swarm enemies, and each section of each arena has a different monster type + status (so you could go through shock beast, poison construct then normal gremlin, for example). There would be NO loot boxes in between arenas, but there would be minerals, and there would be loot at the end of each floor. To make it more interesting, I'd also say only have health regen stations at the start of each floor.
So, if there's no loot between arenas, what's the point?
Well, every 5th floor in the endless zone would be a guaranteed treasure vault, potentially with more red boxes and/or higher chances for rarities. This means that everyone will get their rarity grinder they've been wanting forever, but it's still hard to get to (four straight arenas with limited heals, after clearing all of the T3 arcade), so it wouldn't be too broken.
Possible changes:
- no loot boxes at the end of each floor: exclusively treasure vaults
- no health regens anywhere except treasure vaults
Courtesy of @Fangel
- normal enemies instead of swarm since there are few swarm enemies
- potential for every floor to be an unknown passage
- health boxes after every stage except final
- basically everything in the post directly below this one

From 2013, when I cared enough to write stuff like this- https://forums.spiralknights.com/en/node/74848

what if we had it so it is like a basic arena but with endless waves, and your loot is based on survival time or kills? You also wouldn't be allowed to use SoL is the arena to make it more fair. The amount of monsters, waves, or time, that you survive could determine your loot. And also the loot could be more then just crowns and heat, if you kill enough or survive long enough, you might get things like unbind tickets or UV tickets or even CE.
anyway, just my idea.

A single floor with endless enemies will begin the lag pretty hardcore over time. It also means no boxes, which is the main draw to this whole thing (rarities farming location). While it may be cool for heat and crowns (I would do it for the crowns alone), we have other places which are great for that with very few rarity locations, thus making rarities a focus for this endless core mode.

I like most ideas here. My suggestion is Ze-Epik's idea of the swarm arena with Fangel's idea of the chances of getting different floors (maybe make an arena, a treasure vault and some kind of swarm level like the ones found in D&N and all 3 levels have an equal chance) but I think it should be limited to only swarm monsters as there are no non-infected monsters in the core (I think). I think the arenas should have some boxes that have a chance to drop pickups after every room (4 green boxes and a red box after every room among 5 rooms per arena is pretty decent). Only healing pads at the beginning of an arena and not anywhere else (except the monsters dropping hearts and maybe two health boxes after each room). I also wish for the treasure vault level to look like the one in D&N or the sanctuary but with less boxes than D&N to make it balanced and to only have red boxes (15 red boxes are enough). This idea of loot amount is supposed to be moderately challenging (faster than only doing D&N if you're lucky enough and definitely more fun). I also suggest this to be available to anyone with the rank champion or above and while we're at it I suggest that shadow lairs also become available once you reach the rank champion because of the amount of people I hear of wasting shadow keys while not being able to handle it with a party of knight elites and defenders. The swarm arena should be the same as shadow lairs' depth (D???). For this to be even more balanced, set a cap of 15 floors so you just can't spam it all the time. You should earn it by running through the clockworks till you reach the core every once in a while. New content + free rads + more reason to play arcade, 3 birds with 1 stone as all the devs need is to put all the stuff together (the swarm arena in the mission that has an unknown passage as its last floor is a good example of how swarm arenas should be, use it as a base and change its layouts adding explosive/vortex blocks and some traps). With us having 5 kinds of monsters, 2 types of hazards (souls/turrets) and 3 types of traps (spikes or explosive/vortex blocks) the possibilities are endless maybe even make it random. Sorry for the long post. :3

Having this be available to anyone who has completed Dreams and Nightmares would be a good story-friendly option. Either that, or if a party member has completed Dreams and Nightmares they can activate this in an arcade run, meaning anyone can join so long as one person has completed the mission where the core opens and all.

Forgot to mention the thing about locking the party once you're in. Choose your teammates carefully. Also add a guardian like the one at the entrance of moorcraft manor to prevent anyone whose rank is less than champion to enter. That way, even if you get in, you can't invite people from outside. Not putting restrictions is just asking too much. I suggest doing the same for shadow lairs as well.

It would be nice, but we need more Void enemies for it not to get stale quickly
Something i tought of a while ago was Void Mecha Knights, maybe wielding sworda that inflicy Curse, with The Swarm's pink eye on what was meant to be their " faces ".
If we do a swarm arena, keep in mind that there's only a total of 5 swarm enemies, 7 if you include turrets and souls. Making the standard arenas based off them will not carry over too well.
I would change it up a bit so that the arenas have 2 standard arena parts followed by a third swarm part with rewards after the 3rd part. After the arena you have an elevator that is ??? that has a chance to take you to another arena (50% chance), a treasure vault (30% chance), a "a step beyond" level (10% chance), or an unknown passage (10% chance). From there you just need to make several arena variations and you've got yourself a proper endless arena!
I would say to have health boxes after every arena stage except the final one, with perhaps 4 standard green boxes as well. The final one can have perhaps 10 green boxes. This gets you to about 18 green boxes per arena, a good chance at a treasure vault, but then the occasional unknown passage can show up and mess up your day if you didn't complete the arena's final part without full health.