Do weapon enhancing spells let them hit incorporeal opponents?

Question

So, a party of a Fighter, a Rogue, a Barbarian and a Wizard walks into a ghost city, and meets a hostile Joystealer (or a ghost, or some other incorporeal enemy). The party only has mundane and masterwork weapons (maybe because they're nincompoops, or maybe because they've got mugged), but luckily, they've got a Wizard on their side... Who doesn't have a Ghost Touch or a Magic Weapon spell in his book.

In fact, he has several other spells. He casts Burning Sword (from Spell Compendium) on Fighter's longsword, Keen Edge (PHB) on Rogue's shortsword and Mighty Wallop (Races of the Dragon) on Barb's warhammer.

Do the unlucky adventurers get their 50% chances of hurting their incorporeal foe, or is it up to Wizard to plink that nasty never-do-gooder with his trusty Wand of Magic Missile while his comrades carry him away from the enemy?

This question is strictly RAW, and I need the quotations from the official rules as well

Answer 1

No Hit - no Extra Damage

The incorporeal description says:

MM v.3.5: An incorporeal creature has no physical body. It can only be harmed by other incorporeal creatures, magic weapons or creatures that strike as magic weapons, and spells, spell-like abilities, or supernatural abilities. It is immune to all non-magical attck forms.

All of the spells you mentioned depend on hitting the opponent.

Burning Sword (Spell Compendium):

The enchanted weapon deals an extra 1d6 points of fire damage on a successful hit. Also, on a critical hit, the weapon deals additional fire damage [...]

If there is no hit there is no additional damage.

Mighty Wallop

Mighty wallop increases the damage of a bludgeoning melee weapon by one size category without increasing the dimensions or weight of the weapon

If the weapon does not deal damage there is nothing to be increased.

Keen Edge

This transmutation doubles the threat range of the weapon.

A weapon not capable of hitting the enemy cannot deal crits - thus doubling the threat range would have no effect.

The only question is, whether the spells transform the weapon to a magic weapon.

The description of Mighty Wallop or Burning Sword in no way imply transforming a mundane or masterwork weapon to a magic weapon. These are clearly useless in this case.

There is an ambigous description in Keen Edge:

This spell makes a weapon magically keen, improving its ability to deal telling blows.

While this does not exactly state "The weapon in question is transformed to a magic weapon" it could be implied. Lasting magic properties can only be added to magic weapons. On the other hand we are not talking about creating a magic weapon but about a spell effect. A spell effect can be added to a mundane weapon. Thus, I would judge a mundane weapon with keen edge still a mundane weapon and thus unsuited to harm an incorporeal creature, but I'd say this is a DM's call.

Answer 2

You'll have to give them a magic item or fudge your ghost. If you want to keep the game balance, give them magic weapons that are weaker than their current weapons. I feel like you can also fudge some rules for a blessed item or holy symbol to ward off ghosts. It is my experience that the party will surprise you with their own solution and I think you should support that.

I would like to point out that 3.5 ghosts do not say that they resist or are immune to fire. There is some wiggle room with the rules.

MM 3.5 Incorporeal Can be harmed only by other incorporeal creatures, +1 or better magic weapons, or magic, with a 50% chance to ignore any damage from a corporeal source. Can pass through solid objects at will, and own attacks pass through armor. Always moves silently.

There is nothing stopping the threat of magic fire. So, it might be best to make it a more Role Play than combat. They may want to hide, sneak, or run away and should probably let them. Another fun thing would be to turn one or more of your party into incorporeal creatures or ghosts.

So, yes weapon mod spells can hurt ghosts if your adventurers are ghosts.