Multi biome arenas

[Tyro]

First off, please don't tell me to "just use the search function" without providing helpful links. I'm in a ludicrous amount of pain despite having 4 different painkillers in my system, one of which is morphine. My focus isn't the best.

Is it possible to build an arena which can be used for all bosses, or all bosses save Duke Fishron, or all bosses save Plantera? IIRC actuated blocks don't count for biome determination, so one could theoretically put a bunch of ebonstone/crimstone/lizhard bricks/etc inside the walls and actuate the ones you don't want determining the current biome, but I don't know exactly how to set such a thing up. I'm also not entirely sure you can summon the EoC, EoW, BoC, or other item-summonable bosses in the Underground layer, where it would have to be for Plantera bulbs to spawn.

If that doesn't work, maybe half crimson/half corruption? Summon the boss in one half of the arena, and you're probably close enough even if you move to the other half. That would necessitate a separate arena for Plantera, though, and possibly one for Duke Fishron as well (though from what I understand the best way to fight him is with unlimited flight and no arena, just some healing stations here and there)

 

[Sigma90]

Your best bet might be an arena near the dungeon with crimson/corruption. That'll cover everything except Queen Bee, WoF, Plantera and Duke Fishron. (Queen Bee and Plantera can share an arena in the Jungle.)

But to address your original question...

It should be possible to summon EoW and BoC underground. (That's where the Orbs / Hearts are to smash.) But they need to be within their respective biomes or they'll flee and despawn. I don't think EoC, Twins or Skeletron Prime can be summoned underground. Past experience suggests the item is consumed, but no boss shows up.
WoF needs to be in the Underworld and Skeletron requires the NPC, so they're out of the question. As is the Lunatic Cultist.

If you corrupted / crimson-ed the ocean, you might be able to get an arena for: King Slime, EoC, EoW, BoC, Twins, Destroyer, Skeletron Prime, Golem, Duke Fishron and Moon Lord. I'm unsure if Duke Fishron will enrage in corrupted/crimson oceans.​

Duke Fishron as well (though from what I understand the best way to fight him is with unlimited flight and no arena, just some healing stations here and there)

My strategy for Fishron is to fly in large ovals. With water walking or platforms on the ground, fly up to space. Fishron will enrage in space, but you'll be falling back to the ground by then. Neither Fishron nor his attacks will be able to reach you as you'll be too fast. With the right timing, the Sharknados will spawn on the ground and in space - by the time you've completed a loop, they'll have disappeared. Unlimited flight (e.g. with the UFO) should accomplish the same thing.
Note: This strategy does not work in expert mode.

 

[Tyro]

Spoiler: quote in here

Your best bet might be an arena near the dungeon with crimson/corruption. That'll cover everything except Queen Bee, WoF, Plantera and Duke Fishron. (Queen Bee and Plantera can share an arena in the Jungle.)

But to address your original question...

It should be possible to summon EoW and BoC underground. (That's where the Orbs / Hearts are to smash.) But they need to be within their respective biomes or they'll flee and despawn. I don't think EoC, Twins or Skeletron Prime can be summoned underground. Past experience suggests the item is consumed, but no boss shows up.
WoF needs to be in the Underworld and Skeletron requires the NPC, so they're out of the question. As is the Lunatic Cultist.

If you corrupted / crimson-ed the ocean, you might be able to get an arena for: King Slime, EoC, EoW, BoC, Twins, Destroyer, Skeletron Prime, Golem, Duke Fishron and Moon Lord. I'm unsure if Duke Fishron will enrage in corrupted/crimson oceans.​

My strategy for Fishron is to fly in large ovals. With water walking or platforms on the ground, fly up to space. Fishron will enrage in space, but you'll be falling back to the ground by then. Neither Fishron nor his attacks will be able to reach you as you'll be too fast. With the right timing, the Sharknados will spawn on the ground and in space - by the time you've completed a loop, they'll have disappeared. Unlimited flight (e.g. with the UFO) should accomplish the same thing.
Note: This strategy does not work in expert mode.

I play expert almost exclusively. I'll keep that strategy in mind for my casual character though. Thanks for clarifying that it doesn't work in expert.

Why can't you build npc housing and move the clothier in for Skeletron? Near the dungeon for cultist? I don't need it for first time Skeletron.

 

[BrusselSprouts693]

I play expert almost exclusively. I'll keep that strategy in mind for my casual character though. Thanks for clarifying that it doesn't work in expert.

Why can't you build npc housing and move the clothier in for Skeletron? Near the dungeon for cultist? I don't need it for first time Skeletron.

Npcs won't live in the evil biomes but you can send them over with king and queen statues.

Also EoC works underground, I have no idea about the rest though.

 

[Sigma90]

Thanks for clarifying that it doesn't work in expert.

Doesn't work for me because of the third, teleporting phase. There are probably ways to make it work, e.g. using the UFO, but I have not tried them yet.

Why can't you build npc housing and move the clothier in for Skeletron? Near the dungeon for cultist?

You can build a house for the Clothier, but it needs to be away from the Crimson/Corruption or the housing will be marked as invalid.
Edit: TheWorfer27 beat me to it.