Okay, so you want to play a diabolist. Diabolist can be entered by any caster class, but it's a better choice for arcane casters --- and while you might think a high-Cha sorceror would be a better bet, that's not necessarily true. So let's say you're starting with a wizard. Let's say further that you manage to cast LPB from a scroll, thereby allowing you to enter the class at 6th level instead of waiting for 8th.
The diabolist is the only PrC that's focused on conjuring creatures, so let's talk a little bit about that. At 7th level you can gain Lesser Planar Ally as a spell. Since you took a PrC, you'll have to buy it somewhere as a scroll instead of just gaining it on level-up. And you'll want to purchase Dimensional Anchor, as well... see below. So you do that. Now you can start conjuring devils, right?
Well... maybe. Let's walk through conjuring a simple devil. LPB lets you call up a creature of up to 6 HD. The strongest devil available to you is the 5 HD Bearded Devil. (The 6 HD Shadow Mastiff and Nightmare are also available, but they're not devils, so you don't get any bonuses. Best leave them be for now.) So you fire up your magic circle and start conjuring.
First off, the devil gets a Will save to resist being drawn from Hell. Let us say that you have a 20 Int at this point, and Spell Focus (Conjuration). That gives a DC of 20. So the devil will fail 80% of the time. So far, so good. Oddly enough, there doesn't seem to be any penalty for failure... if the creature makes its Will save, it seems you can just wait ten minutes, redraw your circle, and try again with a different devil. (Has anyone checked whether that's correct?)
Now it gets tricky. "The creature can escape from the trap by successfully pitting its Spell Resistance against your caster level check, by dimensional travel, or with a successful Charisma check (DC 15 + 1/2 your caster level + your Charisma modifier). It can try each method once per day. If it breaks loose, it can flee or attack you."
Dimensional travel, well, you can pre-cast Dimensional Anchor on the magic circle to stop that hole. This requires a DC 20 Spellcraft check, which you don't know the result of. If you've maxed out Spellcraft -- which of course you have -- you have a +15, so you'll make this 80% of the time. The alternate method is to Dim Anchor the devil when it arrives, beating its initiative and then winning a ranged touch attack. Yeah, better go with the Spellcraft check. So the devil is now left with two choices: burn its way out of the circle using its SR, or make a successful Charisma check.
Let's assume you didn't dump Cha because you were building towards being a Diabolist from day one. So you're a wizard with a 12 Cha. The DC of the Charisma check would be 19; your Infernal Charisma makes it 21. The bearded devil has a 10 Cha, so there's no way it's making that check. So, it can only try SR. Its SR is 16, and here's where things get iffy: you're going to need to roll a 9, which means you fail this 40% of the time. That's not so great. Better invest in Spell Penetration (or be an elf). Now you win on a 7 or higher. Still risky but the odds are with you.
Now, if you lose, the devil either departs the scene or can attack you. You don't want to fight this thing, right? So this is where having a friendly party member or two close at hand is good. (And of course, you already have your own Magic Circle cast and are standing inside it.) It's unclear whether the devil escapes back to Hell or is now unleashed on the material plane; if the latter, well, you better hope it goes somewhere far away, because if it stays in the neighborhood it's going to be several sorts of problem.
But let's say you win. Hurrah! Now you can negotiate with the devil. Here's where Planar Binding is very different from Planar Ally. Planar Ally just sets a fixed fee based on the creature's hit dice and the duration of the task. Planar Binding, you *can* offer the creature a fee -- but you don't have to; under the RAW, all you have to do is beat it at an opposed Charisma check. The check can be modified by +0 to +6 depending on the nature of the service and the reward, and you can reroll the check once/day, every day. (Of course, the devil can try escaping once per day, too.) You start with +3 against the devil (+1 Cha bonus is +1, +2 infernal charisma) and under the RAW you can gain another +2 by giving it something to kill, because that's how bearded devils roll.
So as long as you're not asking for anything too strange or onerous, your odds of success are pretty good. "Guard my tower for a week while I'm out of town" would probably be a reasonable request -- though, devils being devils, I'd phrase it more precisely than that. "Go to this building and kill everyone inside, then return home to Hell" would probably work just fine too -- in fact, given that bearded devils are inherently warlike and violent, that would probably be a nice easy check. "Follow me into the dungeon, obey my orders and act as my bodyguard for one day" would be permissible too IMO, though harder.
-- Here's where it gets interesting. There is, AFAICT, no limit to the number of conjured creatures you can have at any one time. So you could call a bearded devil every day until you have a squad of half a dozen of them, and *then* enter the dungeon. Now, at 7th level you'd only be able to call one devil per day -- you're burning two fourth and two third level spells each time -- and since the spell's maximum duration is one day/level, you couldn't get more than 7 devils maximum. And since some will make their saving throws, beat your caster check with their SR, or make their opposed Charisma checks, more likely you'll only be able to get two or three. On the other hand, having two or three melee-brute CR 5 devils marching along with you at 7th level would be pretty sweet, and AFAICT it would be completely RAW-legal.
You have a couple of other interesting options at this level. One is the hell hound. Although it's a Lawful Evil extraplanar outsider, this beast isn't a devil, so you don't get your Infernal Charisma bonus. And it's not as powerful as the bearded devil, being only CR 4. On the other hand, it has only Cha 6 (and Int 6), has no SR, and doesn't teleport. So it's much easier to summon, and no more difficult to control. If you're a little nervous of what a clever DM might do with intelligent, cunning devils, maybe start with a few of these guys first to, as it were, warm up.
Another option is the Zebub or accuser devil. These ugly little creatures are only CR 3, but with at-will invisibility, greater teleport, whispering wind and their infernal eye "playback" power, they're your go-to choice for spying and information collection. You should always have a couple of these little monsters floating around.
Now, at higher levels a whole new set of issues come into play... but let's hold off on that for now. Comments?
Doug M.
