Under the first and second edition rules, a multiclass character with one or two caster classes was a viable option. With the old exponential experience point system, a multiclassed PC only lagged a couple levels behind a single classed PC. A 10/10 wizard/cleric might be travelling in a group of 12th level PCs.
The third edition changed all that. Now levels are additive. In a 12th level group, the wizard/cleric is 6th/6th. The problem is that a wizard/cleric 6/6 is not nearly as potent as a wizard 12, a fighter 12, a cleric 12, or even a fighter/barbarian 6/6.
One friend of mine was very disappointed in his druid/wizard after converting to 3E, and he was right to be.
Under the 3.5 ruleset, however, several prestige classes (PrCs) were engineered to offer a viable model for these old-style PCs. The Eldritch Knight is a fighter/wizard; the Mystic Theurge is a cleric/wizard; and the Arcane Trickster is a rogue/wizard. This was a good thing, in my not so humble opinion. But not every combo was supported with a new PrC. For example, how to model a rogue/cleric? Where is the Divine Trickster?
You could very easily adapt the Arcane Trickster into a Divine Trickster:
- Require ability to cast a third level divine spell, not an arcane spell.
- Require Trickery Domain instead of Mage Hand.
- Require Knowledge (Religion) instead of Knowledge (Arcana).
- Give a priest's BAB progression, not a mage's.
If you object to giving the Divine Trickster the Ranged Legerdemain ability, since it depends on Mage Hand, then replace it with this:
Inspired Trickery -- At level 1, pick one of these skills: Sleight of Hand, Forgery, Disguise, Bluff, or Disable Device. When you use your chosen skill, you may also use one of your daily turning checks as a free action to add a +2 sacred bonus to the skill roll. At levels 5 and 9, pick another skill.
This is a very reasonable way to make a Divine Trickster that will not break the game. Just make sure that you only allow the spells per day to advance in a divine spellcasting class.
BUT ... maybe your DM is a purist, or maybe your RPGA game is Core Rules Only. Can you still play a Divine Trickster without the homebrew revision? You can! Here, let me show you how.
Some Core DMG PrCs let you advance in any spellcasting class, and others grant only arcane casting advancement. The Eldritch Knight, the Red Wizard, and the Archmage, for example, all give "+1 level of existing arcane spellcasting class" with each level. Others, like the Loremaster, the Thaumaturgist, and the Arcane Trickster give "+1 level of existing spellcasting class," without specifying arcane or divine. This means that you could use your Arcane Trickster levels to boost your divine spellcasting!
Now, you still have to meet the Arcane Trickster requirement for entry: ability to cast Mage Hand and a third level arcane spell! The obvious way to do this is as a Rogue 3 / Wizard 3 / Cleric 3 / Mystic Theurge 2 / Arcane Trickster. Three levels of rogue gives you the required 2d6 sneak attack damage and the skills you need. Three levels of wizard plus two MT gives you the third level spell (and mage hand). It's kludgy, but it works.
But there is a way to get to Divine Trickster a level sooner, with better hit dice, saves, skills, and the ability to cast spells in light armor. Start with an evil character, Int 16 at least -- or Int 14 human. Take a level of bard, for four ranks each in Hide, Move, Disguise, Know Arcana, Know Religion, Decipher Script, Disable Device, Escape Artist, Perform, and the ability to cast mage hand. (If you have extra ranks, consider Tumble and Sleight of Hand, IMO.)
Then take three levels of cleric (trickery domain, please), boosting your Hide to seven ranks and your two Knowledge skills to six ranks each. (Other good domains: Travel (for the spells), Luck, or War; other good skills: Bluff and more Disguise).
Take another level of Bard to bring your Hide and Move Silent to 8 ranks each, and throw whatever ranks you've got left into Decipher Script, Disable Device, and Escape Artist. Pick good first level bard spells like Expeditious Retreat and Grease. Add at least one more rank to Perform.
Now we get fancy. Take three levels of Assassin! That gives you a 2d6 sneak attack and second level arcane casting! Also a very sweet death attack, uncanny dodge, and poison use. Follow that up with two levels of Mystic Theurge (MT), boosting your spell casting and giving you that all-important third level arcane spell.
Now, at 11th level, you can take your first level in Arcane Trickster (AT), using it to boost your cleric spell casting. I suggest alternating AT and MT for a couple levels, so that you end up with four or five levels of MT ... for those sweet fourth level assassin spells like Dim Door (unless you get it through your Travel domain), Greater Invisibility, Glibness, and Modify Memory.
If you want to be super-fancy, you can also take a two-level dip into Shadowdancer, mostly for hiding in plain sight, but also for evasion and darkvision. And uncanny dodge from both Assassin and Shadowdancer makes a nice synergy.
What about feats? If you do not go the Shadowdancer route, then you are wide open. Pick to your heart's delight. But there is something to be said for the Shadowdancer prerequisite feats on their own merits: Dodge and Mobility lead to Spring Attack and Whirlwind Attack. With that Exotic Whip proficiency you get for free as a bard, it's nice to be able to attack every enemy within 15 feet. Improved Trip gives you something interesting to do with those whip attacks, and what's more, with your sweet fourth- and fifth-level clerical buffs Divine Power and Righteous Might, your reach doubles to 30 feet, your sickly BAB now equals your character level, and you get a +10 bonus to Strength! That will really knock them off their feet!
Put a glove of holding on your whip hand so that you can put it away at the end of your turn and pull it out at the start of your next turn. Put spikes on your armor so you can threaten adjacent spaces (spaces within 10 feet when feeling Righteous). Hold a pole arm in your off hand -- and grip it with both hands after stowing your whip at the end of your turn -- and you're ready to use your Combat Reflexes when the enemy is moving within 20 feet of you! And did I mention that your Greater Invisibility makes all those attacks into sneak attacks.
Granted, this sweet strategy only really kicks in around 14th level. But before that, there is plenty of fun to be had making tripping spring attacks (your bardic Expeditious Retreat really pays off here) and picking pockets while invisible.
If you prefer not to be evil, remember that as soon as you join the assassins, you can start to have a change of heart. After three levels of assassin, you might well enjoy role-playing your conversion to the good side, if your DM allows you to keep your assassin abilities as an ex-assassin. You may have to promise to use your own death attack only to knock enemies out, not to kill them. Plus all the fun adventures you'll have fleeing the vengeful assassins who come after you for betraying them! Remember, anyone who watches you for two consecutive rounds is an assassin prepping a death attack! You better trip them, just to be safe.
(By the way, you might enjoy checking out my previous thoughts on Assassin / Arcane Tricksters and Mystic Theurges.)