When the party succeeds in lighting the brazier, whichever spirit was used to kindle the Everflame sheds its personality into a weapons of the party's choosing.
These sentient weapons are custom rewards I've designed for this one-shot adventure written by Aviad from Beyond the Screen. You can find my one-shot guide here: https://youtu.be/cWrDbrOsXfk
In the PDF version, I've included multiple versions with different abilities blurred out so you can give the players new handouts as their weapon powers up.