@mr hank the t rex
this is a year old reply, but the asnwer to your question is:
the sulphurous sea is originally from the calamity mod for the game terraria. the lore behind it is that it was corroded by harmful gasses that were produced by a very deep underground civilization called "azafure" after they had reached their own industrial revolution.

but even with this, the place has a flourishing ecosystem thanks to the essence of the goddess of life, silva, who was killed by the godseeker, yharim in his crusade and disposed of in the very bottom of the sulphurous sea when it wasnt corroded back then.

some of these are so stupid and i love them

The bad thing about these arenas is the ecosystem, there is almost nothing and food like batflies are 0.

i wana know what the lore is behind Sulphurous Sea because the water kills you

unfortunatly, I cant use these WONDERFUL arenas because I dont have Downpour, But it looks amazing!

Finally

a fine addition for my unethicl rot experiments

probably the best arenas mod beside testing arenas

MONOLITH CALAMITY MOD!!!!

how the Slug did you make make them soo cool?! I love em!

mabe u coid also add iterator arenas

make the rain interesting and gimcky for each level to add variety

it rained in fridge, im so sad

chilled rooftop is in metroppilis

sulfurus sea has to be calamity reference

how come the outer expance is frozen??

Well, that's sick! It's a really cool arena!

totally a reference

Is the Void Island a reference to Risk of Rain 2?

bro I was watching the development of the one on the thumbnail
it's insane

NAAAAAAAAAAH THAT LAST ONE IS IN A MOD

truly a gem

snowy outer expanse???

Outer Expanse in the blizzard? Sign me the FP up.

@jacksondaxhacker Everything works fine in my testing... Maybe a problem with your mods?
Try disabling everything except required mods and see if that helps.

For some reason the slugcats aren't spawning in properly when I play

these are high quality arena's

Beautiful