What happens if a Rainbow Servant takes levels in Mystic Theurge?

Question

When a Rainbow Servant hits level 10 they gain access to all nondomain Cleric spells. All spells that do not appear on any other spell list they have are cast as Divine spells. This means that, if they have the skills and have learned 2nd level spells, they qualify for the Mystic Theurge Prestige Class.

But what happens when you actually start to take levels in it? The text says:

When a new mystic theurge level is gained, the character gains new spells per day as if he had also gained a level in any one arcane spellcasting class he belonged to before he added the prestige class and any one divine spellcasting class he belonged to previously.

What it does not say however, here or elsewhere, that these classes have to be different classes. Do you get one level in Wizard/Warmage/whaever for being an Arcane caster, then ANOTHER level for being a Divine caster as well? The text for the Rainbow Servant says the following:

Such spells are cast as divine spells if they don’t appear on the sorcerer/wizard or bard spell lists.

So it comes down to these questions:

• Does being able to cast Divine spells qualify you as a Divine Caster, or is there more to it than that?
• If it is, what happens when you take levels in Mystic Theurge like this? Do you go up one level or two?
• What happens if this means you go over 20th caster level? Do you keep gaining spell slots like a level 20+ character, or does something else happen?

Answer 1

RAW: Ambiguous

The rules are not clear on what, exactly, constitutes an “arcane spellcasting class” or a “divine spellcasting class,” probably because initially it was obvious. By default, assassins, bards, sorcerers, and wizards were the arcane spellcasting classes, blackguards, clerics, druids, and paladins were the divine spellcasting classes. There was no ambiguity: the former are the classes that cast arcane spells, and the latter are the classes that cast divine spells. Easy.

Then they printed things like Alternate Source Spell, Rainbow Servant, Sha’ir, and Southern Magician, which introduced ambiguity that hadn’t existed before. In these cases, you have spell slots from one class being used for either arcane or divine spells.

Does this new feature suddenly make the class into an “arcane spellcasting class” or “divine spellcasting class” where it wasn’t before? There hadn’t ever been a strict definition before, and they didn’t print one at this point, either. Some of these effects seem to try to include wording that prevents this kind of thing, but much of those rules are also unclear. For instance, consider this from Southern Magician: “The actual source of the spell's power doesn't change,” which Customer Service interpreted as preventing entry to mystic theurge. But it doesn’t really say that, does it? It says something about power source, which is unclear.

Unfortunately, there’s no direct, rules-as-written, “as it says on page xyz of Complete Shenanigans” kind of answer to this question.

Recommendation: Never

RAW is ambiguous, but what’s going to work well in-game is not: never, under any circumstances, should one be allowed to advance wizard spellcasting faster than the wizard does. That should never, ever happen in any game, and if you’re going to allow it you might as well allow Pun-pun.

Allowing these sorts of tricks to qualify for mystic theurge, and other prestige classes and feats that require one type of spellcasting or the other, is pretty clearly legal, RAW, and also usually far less troublesome. The only exception I’d be likely to make is the dweormerkeeper from Complete Divine’s web enhancement, but then I’d probably just ban that class outright.

Even allowing a divine-only prestige class to progress wizard spellcasting is almost-always not a problem. It’s the double-progression that should never, ever happen.

Answer 2

Here's an interesting way you could choose to interpret it that sidesteps the issue: The class that grants divine spells is Rainbow Servant, via the class features to expand your spell list. Rainbow Servant does not grant spells per day, so adding spells per day as if you had gained a level in Rainbow Servant does nothing. Therefore, you only get the boost to Wizard once.

True, you could argue that Rainbow Servant has a clear pattern to granting Wizard spells/day levels, but there is no explicit text saying level 11 of Rainbow Servant would have granted another +1 to Wizard spells/day, and in any case there's no ruling saying that the transitive property applies here even if it did.

Answer 3

You can take Mystic Theurge, but...

There are four interlocking issues that keep this from being a game-breaker. But you're right that the requirements of the Mystic Theurge PrC do not require your spellcasting abilities to come from any place in particular. They can come from the same class, or even more exotic effects if you can make it happen. But the results aren't what you might suppose...

1. Bonuses simulate having better abilities, but don't actually grant better abilities. Most of the time, this isn't important, but edge cases pop up from time to time where it matters. You've found one of those edge cases.
2. You cannot apply spellcasting boosts to a class that doesn't have a spell progression. This follows from the issue above. For example, a Wizard/Cleric can't level-dip in Fighter and Mystic Theurge, then take Eldritch Knight and apply the Eldritch Knight's spellcasting boost to Mystic Theurge. Rainbow Servant (much like Mystic Theurge and Eldritch Knight) does not grant you a spellcasting progression: it only boosts your existing ones. Thus, you can't apply spellcasting boosts to it.
3. Wizard is not a divine spellcasting class. Rainbow Servant grants characters an unusual bonus that lets arcane casters use divine spells, but it does not grant them a new spellcasting progression: it only lets them mix some new spells in. It's explicit about this, in fact: you still have to use your arcane slots to cast your divine spells. Thus, it does not turn your Wizard class into a divine spellcasting class; it just uses an unusual bonus to broaden your access a bit.
4. If something would happen but has no valid target, then it fails to happen. This is what causes the real pain, as we'll see in just a moment.

So, you've got your Wizard/Rainbow Servant, and you take your first level in Mystic Theurge. You apply the arcane boost to Wizard as normal, which makes sense. But the divine boost has no valid targets: Wizard isn't a divine spellcasting class, and even if we were to decide that Rainbow Servant is, it has no progression and therefore can't be boosted. Since the boost can't target anything, it's wasted.

This is, shall we say, suboptimal. You could do it, but it wouldn't make a whole lot of sense. If you could find a class that gave you an arcane progression and a divine progression, then you could apply both boosts to it and have the sort of fun you describe. But I don't know of any such classes off the top of my head, and Rainbow Servant doesn't make it happen.

Answer 4

RAW: using the exact wording of the Rainbow Servant class, yes.

For all conceptual purposes, Rainbow Servant turns a purely arcane caster into both an arcane and divine casting class, as the ability granted by the prestige class states that you use your original arcane class' spell slots to cast divine spells. (Yes, I know there is a heavy debate on the nebulous definition of "Arcane spellcasting class" VS "Divine spellcasting class", but for practical reasons, an Arcane casting class is a class that allows you to cast arcane spells. A Divine casting class is a class that allows you to cast divine spells. Again, that is the practical/logical interpretation of the term, and likely has no "official" published evidence to declare either way.)

This being the case/logical assumption, it would follow that the Rainbow Servant modifies any qualifying arcane spell caster into a dual-sourced casting class. Following that logic/assumption, the wizard (or other qualifying arcane-spell capable spellcasting class) would indeed qualify for the spell-casting requirements of Mystic Theurge, and would also qualify for ten levels of double spell progression. Congratulations, you have potentially shattered any concept of balance for spellcasting in your game.

This being said, that decision ultimately rests with your Game Master, as "rule 0" can potentially override any written rule in the game, and any GM with an eye to keep a party balanced with each other would (most likely) disallow that particular combination. I do not have evidence to support the following statement, but I believe this was one of those circumstances none of the designers anticipated being a possible issue at the time of publication, and so no regulation or counterbalance was ever formulated while 3.5 was still in publication. I hope this helps.

And, always ask your DM before attempting a build you need to question the validity of. They may save you time and energy spent working out a min/max build by telling you "no" before you do all the work, rather than telling you "no" after you put all the work in.

Answer 5

RAW

Technically, 'Divine Spellcasting' can be defined as 'casts divine spells'. That's the.. most logical reading of it. And a Rainbow Servant Wizard totally does do that.

I can't see a RAW wording/definition reason why he would not qualify that does not also disallow multiclass Wizard/Clerics.

That said, it's vastly, vastly outside the RAI.

Playing The Game

Wizards are already completely ridiculous. Their power advances quadratically, and insanely. Sure, the earliest you can pull this trick is level 12. But there's just.. no need? Maybe in some crazy RAW arena style game or something, or 'build the most broken thing you can' it could work. In any game with other players, you're taking the 'Wizard Problem' and giving it NITROUS BOOSTERS.

Is this really wise?