Mysteries and Soulmelds: Theurgy?

[Xuldarinar]

I've been looking into Tome of Magic and Magic of Incarnum lately, and wanted to ask a simple question. Whats the best one can do to combine mystery-using with meldshaping?

[Big Fau]

Soulcaster theoretically can work with Shadowcaster entry, but it wouldn't be very good due to Shadow Magic's inherent low-power.

[Verditude]

Well, by RAW, you don't qualify for Soulcaster since it specifies arcane spells, but if you can get that approved you have a pretty good theurge build. Shadowcaster 3/Incarnate 2/Soulcaster 10/Legacy Champion (advancing Soulcaster) 5 nets you CL 17 and MsL 16. Soulcaster requires 8 ranks K:Arcana, so you're not getting in earlier than that.

Note again, RAW, this doesn't work; the way ToM words how shadowcasters interact with prestige classes specifically makes an exception for the mystic theurge, not theurge-type classes, but it shouldn't be too difficult to get your DM to approve this, if he's familiar with both subsystems.

[Xuldarinar]

Thank you. The soul caster route is certainly an option, for dm who allows adaptations. Later perhaps i'll make a Mystery-user/meldshaper theurge type PrC and see if anyone would welcome it to the table. Best I got in the realm of homebrew for that are these:
IMPROVED SOUL STEEPED IN SHADOW [INCARNUM]
Prerequisite: Con 15, Must have been exposed to shadow, Knowledge (the planes) 8
Benefit: Once per day you may invest essentia into this feat. Upon gaining this feat you select a 2nd and 3rd level mystery. When you have essentia invested in this feat you may use these each a number of times per day equal to essentia invested. This invested essentia remains invested for 24 hours, or until you have used all of your uses for your mysteries. You cannot invest essentia in this feat if you do not have essentia invested in soul steeped in shadow, nor can you invest more essentia in this feat than you have invested in soul steeped in shadow.
You gain 1 point of essentia.

SOUL STEEPED IN SHADOW [INCARNUM]
Prerequisite: Con 13, Must have been exposed to shadow, Knowledge (the planes) 4
Benefit: Once per day you may invest essentia into this feat. Upon gaining this feat you select a single fundamental and 1st-level mystery. When you have essentia invested in this feat you may use these each a number of times per day equal to essentia invested. This invested essentia remains invested for 24 hours, or until you have used all of your uses for your mysteries. The Difficulty Class for saving throws against any mystery cast using this feat is equal to 10 + the mystery level + your Constitution modifier (or Wisdom in the case of an Incarnate). Your caster level for mysteries cast through this feat is equal to your meldshaper level.
You gain 1 point of essentia.

TRUE SOUL STEEPED IN SHADOW [INCARNUM]
Prerequisite: Con 15, Must have been exposed to shadow, Knowledge (the planes) 12
Benefit: Once per day you may invest essentia into this feat. Upon gaining this feat you select a 4th and 5th level mystery. When you have essentia invested in this feat you may use these each a number of times per day equal to essentia invested. This invested essentia remains invested for 24 hours, or until you have used all of your uses for your mysteries. You cannot invest essentia in this feat if you do not have essentia invested in improved soul steeped in shadow and you cannot invest more essentia in this feat than you have invested in improved soul steeped in shadow.
You gain 1 point of essentia.

It is a shame though, there isn't a RAW way to mix the two effectively.

[Chronos]

One way is to take most of your levels in Shadowcaster, with two levels in Chameleon as soon as you qualify for it, and a few assorted incarnum feats for essentia. Use your Chameleon floating bonus feat for Shape Soulmeld, shape that meld, then the next day change the feat to a different meld, and so on, until you have ten melds of your choice shaped (note that you keep soulmelds indefinitely once shaped, until you deliberately unshape them or something forces it to unshape, so losing the feat you used to gain it shouldn't be a problem).

You don't gain any chakra binds this way, but given that you were probably planning on using magic items anyway, that's not such a big deal. And your essentia capacity won't be quite as high as an actual Incarnate's would be, but it still scales with your total character level, not your meldshaping level.