Pretty self-explanitory, I'm making a homebrew campaign, and my BBEG's right-hand man needs a way to have permanent, 24-7 access to the Plane of Fire to siphon off heat to power *insert evil world-ending machine thingy here*. First off, is this possible, and second off, if it is, how would he accomplish this? Am I overlooking something?

Quote from Great_Axeblade >>

Pretty self-explanitory, I'm making a homebrew campaign, and my BBEG's right-hand man needs a way to have permanent, 24-7 access to the Plane of Fire to siphon off heat to power *insert evil world-ending machine thingy here*. First off, is this possible, and second off, if it is, how would he accomplish this? Am I overlooking something?

 gate perhaps with a contiengcy in place for stopping anti magic 

Thanks for the help! I had no clue that spell existed! :)

I think a Plot Device is what you want.

Perhaps ;)

Gate is what you're looking for.

Near a volcano I would imagine.  For a natural occurrence.  Otherwise as someone else said, a plot device that opens one.

Your BBEG's lair has been mapped out

Take my like and get out :D

Quote from Great_Axeblade >>

Take my like and get out :D

To be serious, the DMG actually gives you broad latitude as well as ideas on how to limit (if you want) a planar portal.  Something volcanic makes sense.  I've heard stories of IRL mine fires that burned for years or decades.  Just to throw a creative freebie at you because I was thinking of the jaws of dead elemental but that's really not a thing, how about a place where a might fire elemental fell leaving behind an ash pit, however either "naturally" or with the right incantation, the ash pit works like quicksand and drags you into the elemental plane who's essence scorched the pit in the first place (so it can be used for transport but also the disposal of enemies).  I imagine the planes of Earth and Fire may touch in a plenty ash filled place, call it the City of Cinders or something.  

Quote from Great_Axeblade >>

Pretty self-explanitory, I'm making a homebrew campaign, and my BBEG's right-hand man needs a way to have permanent, 24-7 access to the Plane of Fire to siphon off heat to power *insert evil world-ending machine thingy here*. First off, is this possible, and second off, if it is, how would he accomplish this? Am I overlooking something?

 Yes. By simply stating that your BBE has one of those, it makes it true. Remember, the books are all about what the PCs can do. Villains play by their own rules. 😉

Right. Some of my players are far more experienced than me, so I just wanted a plausible excuse lol :)

Maybe the evil side caught a powerful elemental? I know of a published adventure where some derro basically are using a fire elemental as the source of power for their smelting operation in an old inactive volcano. Basically the head derro wizard opened a rift via insane rituals (that the party likely can't or won't replicate) then lured and trapped the biggest elemental that wandered in.

Quote from Great_Axeblade >>

Right. Some of my players are far more experienced than me, so I just wanted a plausible excuse lol :)

 Don’t give them one, they don’t need it. In fact, there should be things the party never gets to understand. Not only does the mystery maintain the suspense, it also increases verisimilitude. 😉

Quote from Great_Axeblade >>

Right. Some of my players are far more experienced than me, so I just wanted a plausible excuse lol :)

 You don't need a plausible excuse. It is there because you said so. 

You can dress it up and have a flickering portal, or runes engraved in the floor, or a painting on a frame that looks very realistic, and then you see something in the painting move.

The reason for it existing is because the BBEG needs it. The only plausible thing the party needs is a way to get rid of it (maybe).

Another way of explaining it is that most game worlds, the party aren't "myth busters".  There isn't a "science to magic" where you present a magical phenomenon that can be reproduced by PCs from spell lists so they can confirm the phenomena is legit or not in the game world.  That's not how plausibility works in D&D for the most part.  Suspension of disbelief, "rationale" gamers aside, is frankly more art than science.  As long as a novel magical phenomena works consistently _with itself_ (meaning, you don't really need precedent for it to exist in your game world) you should be good.  Maybe the souls of many bards are trapped in some vessel, cursed to perform the Heat Meiser song in soul servitude into perpetuity, or the PC figure out and figure out how to free them and the spirit of Christmas from their confines (but that's gotta be high risk and the consequences being the PCs themselves being trapped in a perpetual Heat Meiser song and dance performance until their bodies give out and their souls too get confined in the song vessel.  I recommend a phonograph or gramophone for maximum anachronism.

[caveat: there are "simulationists" in TTRPG-land, but when most players are talking realism, they're talking more about emotional suspension of disbelief than "Sim fantasy" where monetary/fiscal economy, supernatural physics etc. are all hashed out.  I think for your average 5e player Colville's Strongholds and Followers is probably as far as most players would really want to go, and for many other players even that work is a bit much.  Back to what I consider "the good part".] 

For example, my party has acquired a duck named Philip through shenanigans at a Magical weapons laboratory.  They know the duck is named Phillip because whenever anyone refers to Phillip as a duck or anything other than Phillip, the duck calmly asserts "My name is Phillip."  Speak with Animals, etc will only glean that info from Phillip.  Why is this duck imbued with the ability to assert "My name is Phillip" in common?  I don't even know that.  But my party accepts it.  The how's and why's of a permanent or at least established portal to an Elemental Plane really aren't that different on a creative level.  Just make sure you know how it works, and it works in a fair manner and any exploits a BBEG may have access through it are likely accessible by the party, etc.  Basically be more keen in on how much (living/unliving) material can move through the portal at a time (maybe by hit dice or say 6 medium humanoids with more or less adjusted for larger or smaller being, or objects of a certain weight.  Maybe all but magical metal is diverted in the passage and arrives in the fire plane's smelting pools etc.  Have fun with it, and have fun with your party's expectations.

I'm not a big fan of JJ Abrams "magic box" theory of story telling because I think his creative posse and Hollywood have serious hurt narrative story telling in its use.  But that's for contained narrative works.  For something like a D&D campaign, it's very effective where as far as the world's workings go, the DM only needs to know enough to present in a fashion that leads the players to be able to say "ok, then I will..."

I like the City of Brass, this thread makes me want one of my games to go there via a Heat Miser (Heat Miser would be a great "Season 2" villain if a campaign stays in Icewind Dale after Rime of the Frost Maiden.  "Sorta like last adventure's challenge, but the opposite.").

All great ideas!

I would probably try to have someone pray to a god to open the gate and hold it open for me.  A gate spell is pretty advanced, right?  There have to be gods sympathetic to your cause that would help to some degree, right?  If the BBEG consists of many members, then the petition to the deity should carry more weight.  However, they might have to "pay the price" to keep it open.

Well, I wanted there to be several portals, with my late-game party being able to eventually capture one for their own use.

Personally I think you just need some netherrack.