I've got a llittle more left to post up (a couple magic items and epic xenotheurgy) but I'll leave it at this for now.
I need sleep.
Edit: actually, I'll take this opportunity to talk a bit about what on earth I was trying to accomplish with this. In short, I wanted to make an over-balanced magic system, a system that anyone could theoretically use but that was too risky to be a real boon for anyone other than a specialist.
An afflicted/blessed xenotheurge is akin to lycanthropecy or vampirism, a negative condition that comes with a bunch of perks. However, unlike the two aforementioned conditions, xenotheurgy has drawbacks that are impossible to ignore and that hopefully keep them from becoming overpowered.
The base mechanics of xenotheurgy combine Zeta Kai's Biomage with the Tome of Magic Truenamer. I toned down the biomage death down to a week of uselessness (to keep players from running one character into the ground and rolling up a new one, ugh!). With the Truenamer, I toned down the law of resistance, turned the skill check into a saving throw, did away with the law of resistance and let the power still work with a failed roll. I put lots of work into making sure that things stayed nicely balanced.
However, there is one thing about xenotheurgy that all DMs should know before including/allowing it in their campaign. Although I worked hard to keep it balanced, this system is still more than capable of being disruptive to a campaign.
Both disturbances and incursions can ruin the element of surprise and attract angry mobs. Most of the time, this isn't a big deal. If the player is mature enough (or is good enough a role player) to try to take care of these problems without drawing attention, things work. Even if things get out of hand, having to walk around a town rather than through it likely won't stop a party from slaying the dragon in the mountainside on the horizon (or the xenotheurge can remain hidden somewhere while others go into town). There are two specific instances when xenotheurgy becomes a hindrance to game flow.
1. Some players simply aren't adult enough to handle xenotheurgy. They will run around with incursions and disturbance on trying to scare townsfolk. Eventually, they will probably bring the party so many woes that they decide to kill the guy themselves. Remember, there is a line between tragic antihero and jerk with a deathwish.
Then again, the same can be said for warmages that destroy hamlets for fun. The problem here is likely with the players but xenotheurgy gives such players tools to cause more mayham than most other classes.
2. In more political and diplomatic campaigns, xenotheurges fit in about as much as warmages. Once again, this isn't a particular problem with xenotheurgy as a mechanic but is rather a matter of the campaigns mood and speed.