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.

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

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 ".