We all know that the undead resistances to almost every damage type is an
arbitrary setting, and the settings have not been changed in years. They've
just "always been there". Now until BatMUD goes all D&D by making undead only
vulnerable to magic attacks (and, might I add, that would royally suck if
every random undead required a red glow weapon) they're the standard by which
the nonliving resist attacks.

Fire is stereotypically an undead-hunting weapon, that's true. Vampires aren't
too fond of it, the mummy sure didn't like it, and Franeknstein's
monster...wasn't really undead, so he doesn't count. But at the same time,
bone doesn't burn particularly well, rotting flesh is kinda soggy, and I have
no idea if ghosts are flammable or not. In a perfect MUD, each individual
monster would have its own unique, nonrandom resistances to damage. But that's
asking quite a lot of our area and lib coders. Until those settings arrive,
I'm willing to leave fire as one of undead's weaker resists. At least
channellers don't use psi attacks.

Shinarae Lluminus