Adding spells to enchanted weapons

Question

So, quick and simple. D&D 3.5 for relevance Can you enchant a 1/day spell onto a pre-enchanted weapon. If so, is it a cost increase, or + increase?

Lets say I have a +3 longsword. I go out and I put the Vanishing enchantment on it (+8000 MIC 45) Now it's price point jumps up, but I can still put +7 enchantment "levels" on it. Can I go and get Fireball 10 1/day (+12,000GP value according to craft item tables. 10 x 3 x 2,000 / ( 5 / 1 )) put on it and still have +7 levels of enchantment to put on or...?

Would a fighter require a UMD 30+ (20+caster level) to cast said spell or can s/he just use it as a standard action?

Answer 1

You seem to have two related but separate questions, so I'll tackle them somewhat independently.

Can I add Vanishing to an already-magic weapon; if so, what is the cost and what are the later options available?

Yes, you can add new abilities to a magic item. The cost to do so is the cost of the "new" item minus the cost of the "old" item. So, adding the Vanishing property to a magic sword would cost 8000 GP (and would take 8 days).

Since Vanishing is a straight GP cost and not an enhancement equivalent, you would still be able to add 7 enhancement "levels" (and any number of straight-GP-cost enchantments, Shadowstrike, Sizing, or Slow Burst (MIC p43), for instance).

Can I add a Use Activated spell to my sword, and how would a Fighter use it?

This is more of a "GM call" question, but the rules for an item with multiple different abilities would probably come into play:

Abilities such as an attack roll bonus or saving throw bonus and a spell-like function are not similar, and their values are simply added together to determine the cost. For items that do take up a space on a character’s body each additional power not only has no discount but instead has a 50% increase in price.

Since you're using the Use Activated or Continuous price (CL x Spell Level x 2000, divided by 5 to be 1/day), your Fighter would simply have to follow the Use Activated item activation rules. Basically, he'd have to say a word and/or wiggle the sword just so and the spell in question ("fireball", in your question) would go off. In any case, it'd probably be a standard action which may provoke an attack of opportunity (some Use Activated items do, some don't).

And, since this secondary ability is another straight GP cost, it wouldn't use any of the remaining 7 enhancement levels available.

So, your fighter could, in principle, have a +5 Brilliant Energy, Slow Burst, Sizing, Shadowtrike, Vanishing longsword that allows him to cast Fireball, True Strike, and Blur, each once per day. It would be ridiculously expensive, but it would be legal under RAW.

... any GM that let you actually build such a monstrosity should probably have his head examined, though.

Answer 2

You can, but it may cost you

What you’re doing is combining two separate magic items (unless you find a weapon property that explicitly grants fireball 1/day), since the guidelines are for a separate magic item. Combining a second magic item into a magic item costs what the second item costs, plus 50% the cost of the lower-value item. In your case, your 26,000 gp +3 vanishing longsword and your 12,000 gp item that fireballs combine for not 38,000 gp, but rather 44,000 gp: an extra 6,000 gp, or half the cost of the item that fireballs.

Now, the crafting guidelines are just that: guidelines. Your DM has to review what the guidelines say, and make a decision: yes, no, or yes-but-for-a-different-price. Were it me, I’d probably waive the 50% penalty for combining the items, but that’s a question for your DM.

Anyway, this does not affect the enhancement-equivalent of your weapon, just like vanishing does not. Your weapon is still a +3-equivalent, which means further enhancement bonuses or enhancement-equivalent properties are adding on to 3 for figuring out their value, and you can still go all the way up to +10-equivalent (i.e. have another +7-equivalent to add). However, in addition to the limitation of +10-equivalent, there is also a limit of 200,000 gp for any pre-epic weapon. The vanishing definitely counts towards that limit; the cost of adding in the item that fireballs is less clear; you’ll have to ask your DM.

A wand of fireball in a wand chamber would be massively superior

If you can activate it (at least a single level in a class that eventually gets fireball, or DC 20 Use Magic Device check), a wand of fireball is massively more economical. You could even get an eternal wand of fireball,^MIC for fireball 2/day, if the 50 charge thing worries you.

Then Dungeonscape allows you to modify any weapon for 100 gp to add a wand chamber, allowing you to have the wand in your hand, ready to go, any time your weapon is.

Also, fireball is a really bad spell

Fireball is a very poor spell, and very much not worth 12,000 gp to get 1/day. 12,000 gp could improve your weapon enough to deal far more damage than a fireball is likely to do, several times a day.