Can Gated Fiends/Celestials Die Permanently?

Question

I am specifically trying to reconcile the wording from the DMG, p.47, with what I know of how planar creatures work.

Traveling through the Astral Plane by means of the astral projection spell involves projecting one's consciousness there, usually in search of a gateway to an Outer Plane to visit. Since the Outer Planes are as much spiritual states of being as they are physical places, this allows a character to manifest in an Outer Plane as if he or she had physically traveled there, but as in a dream. A character's death- either in the Astral Plane or on the destination plane- causes no actual harm... Thus, high-level characters sometimes travel to the Outer Planes by way of astral projection rather than seek out a portal or use a more direct spell.

Which led me in turn to the astral projection spell itself:

If you enter a new plane or return to the plane you were on when casting this spell, your body and possessions are transported along the silver cord, allowing you to re-enter your body as you enter the new plane. Your astral form is a separate incarnation. Any damage or other effects that apply to it have no effect on your physical body, nor do they persist when you return to it.

The wording clashes a little, but the intent seems clear - if you use astral projection to travel to a non-Material Plane, you work the same way a summoned fiend, fey, or celestial works on the Material Plane. You aren't permanently killed so long as you used the Astral Plane to travel to the plane you're currently wandering around on.

And this is where my question comes in - what about gate?

The DMG is pretty clear that other methods of planar travel, such as plane shift, don't provide the protection that astral projection does. I'm not going to go into whether a creature that can shift between planes innately possesses the same protections - that sounds more like a discussion than a straightforward question. I'm just interested in this one spell, and its implications. Normally, fiends, celestials and fey summoned to the Prime Material simply get sent back to their native plane upon destruction, and the only way to kill them permanently is to travel to their plane and end them there. Could you use gate instead to kill them permanently on the Prime Material Plane?

Answer 1

No

To open, lets look at a sample of the rules that say you cannot permanently kill such a creature outside of their home plane...

The only way to truly destroy a demon is to seek it in the Abyss and kill it there.

MM 51

Devils that die in the Nine Hells are destroyed forever

MM 67

Only on its native plane can a yugoloth be destroyed permanently

MM 311

Of note: Angels in the 5E MM do NOT have this protection. Weird as it may seem, it is actually easier to kill a Celestial than it is to kill a Fiend.

The nature of Astral Projection is that your Physical Body and your Astral Body are separated. Your Physical Body is left behind on your 'Home' Plane while your spirit goes walkabout.

Bringing Fiends and Celestials to the Prime doesn't work like that. When you summon one, it isn't just their spirit you are summoning while their true body is left behind on their home plane, you actually summon them.

The descriptive text for Demons on MM 50 says

Wherever they wander across the Abyss, demons search for portals to other planes.

The descriptive text for Devils on MM 66 says

Devils are confined to the Lower Planes, but they can travel beyond those planes by way of portals or powerful summoning magic.

In both of these cases, it is explicitly mentioning 'portals' as a way that Fiends find their way to the Prime. Portals are a way to physically move from place to place, not a way to send your spirit somewhere without your body tagging along.

Gate, in essence, is a portal that you create between where you are and anywhere else that can suck something through if you know their True Name.

Thus, a Demon who found a Portal to the Prime Material Plane and a Demon who was called to you through a Gate both, effectively, arrived on the Prime in the same way. They are both entirely and physically there. And because they are not on their Home Plane...they cannot be permanently killed.

Simply put...Astral Projection is the exception to interplanar travel rules - it is not the general rule. Plane Shift, which physically moves you to another plane, is only 7th level--compared to the 9th level Astral Projection. Astral Projection is special because it gives mortals the same degree of insurance when plane-hopping that Fiends and some Celestials enjoy naturally.

Just as a cautionary note, though: if you are Astrally Projecting, watch out for 'Silver Swords' (most commonly wielded by the Githyanki). Those can still kill you for real.

To sum up:

tl;dr:

The books say that a Fiend cannot be permanently killed on a plane other than their home plane. How they left their home plane doesn't matter.

Astral Projection is an incredibly powerful spell because it lets an Adventurer mimic that same feature via magic.

Answer 2

The Gate spell clearly states it drags the entity through a gate.

When you cast this spell, you can speak the name of a specific creature (a pseudonym, title, or nickname doesn't work). If that creature is on a plane other than the one you are on, the portal opens in the named creature's immediate vicinity and draws the creature through it to the nearest unoccupied space on your side of the portal. You gain no special power over the creature, and it is free to act as the DM deems appropriate. It might leave, attack you, or help you.

This says to me that you bring the physical form to that realm of existence. Similar to Plane Shift, you are fighting the true form of the entity. This to me is further cemented in the fact for Gate to work, you must use the entity's true name. This is usually a sign of power over them, however Gate specifically states that you hold no power over the entity. The only explanation that makes sense to me is that the true name gives you the power to draw the true form of the entity to that plane, which then should be able to be killed. When looking at things like Find Familiar, it states this spirit takes on a form, which is why it returns. It doesn't use it's true form. To further this point, most instances where you summon or conjure other creatures, like celestials, fey, animals, and so on, the verbiage is usually "it takes the form of", or like in the case of an elemental it uses pre-existing elements of it's type near you to posses in a sense. It doesn't bring its own fire/rock/air/water to the plane from the elemental plane.