D&D General need an idea for how to find a "celestial" weapon

[Bird Of Play]

Thanks everyone!!

I really enjoyed the ideas provided here. In fact, I'm going to take'em all in one way or another, and put them to use.

The idea of a particular storm in the sky being a celestial battle of angelic and demonic shapeless energies is so cool. I will use it either for the will-o-wisp or for another demonic/angelic encounter; it will depend on the players actions (having them see a star fall from the sky will get them to move, if they don't find the area where the will-o-wisp is).

And.... I guess it's not a will-o-wisp but a lantern archon. Interesting, I didn't know or remember about that specific creature..... but it fits much better than the will-o-wisp (which my olde 2nd edition manual described as kind of evil anyway). A lantern archon, but the players believe it's a will-o-wisp.

The idea that when the archon enters the sword, the blade goes like SPROING and becomes some sort of odd fractal thing such as this

https://images.fineartamerica.com/images-medium-large-5/the-sword-a-fractal-abstract-ann-garrett.jpg

is awesome.

I'm gonna lay down a plan on this and see how it'll work.

 

[Quartz]

The idea that when the archon enters the sword, the blade goes like SPROING and becomes some sort of odd fractal thing such as this

https://images.fineartamerica.com/images-medium-large-5/the-sword-a-fractal-abstract-ann-garrett.jpg
is awesome.

Not my cup of tea. Do have that form appear for a moment as the archon enters the weapon, and perhaps on special occasions but keep the everyday form of the weapon.

Something else you might like to hold in reserve: perhaps the PCs are fighting valiantly against the demon but are heading for defeat. So the archon heads for the PC most in danger of dying and merges with their armour, not their weapon. This provides a Sanctuary or Protection from Evil effect.

 

[AtomicPope]

As far as Demons, there are two you should greatly consider for your campaign:
1) Dybbuk - incorporeal demons that possess humanoids
2) Maurezhi - demons that devour humanoids and steal their form and memories

Both are fantastic. I just remembered them. I used them both for an Evil Dead one-shot I ran on Halloween a few years back. Dybbuk are awesome! Their "violate corpse" ability is a lot of fun and offers up great opportunies for roleplaying. I modified the Dybbuk to make them a little more like the the movies. This is it here:

Infernal Wounds - unarmed strikes by the Dybbuk caused an additional +1d6 necrotic damage. The target creature's maximum hit points is reduced by this amount. This reduction lasts until the target finishes a short or long rest.

(Since most creatures don't have an unarmed attack I just have them make a Dex attack for 1d4+4 bludgeoning and +1d6 necrotic.)

 

[Bird Of Play]

I like these ideas too!
Yes, the archon might actually merge with an armour too..... that's pretty unique! I actually wonder why I didn't think about that option.
I'll let the rng decide, whoever is in the most danger will end up being the one with a magical weapon or armour. (.....Or maybe I'll have the archon merge with the gnome's beloved pipe, that'd be hilarious.)

As for then dibbuk and maurezhi.... I'm gonna keep those names in mind.