Did you roll your HP or take the average? Your hp value seems a little low, even for having a d6 hit die and low con. Did you remember to give yourself double-max HP at first level?
Also, just because I got my cleric cohort done doesn't mean I'm quite satisfied with it. It's still rather squishy and can't really contribute to combat very much, though if it can last until it gets higher level spells it should manage to be an effective powerhouse as usual. For now it's vulnerable and I'm still unsure whether to bother with cloistered cleric or just go general cleric. In the interest of saving time, however, I'm willing to keep it as-is.
Also, Takanaki, any updates on your ideas?
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On another note, can a spellthief steal the ability to cast a cleric's spontaneously converted spell? For instance, could it steal a prepared 1st level spell, swapping it out for cure light wounds as the cleric would? Essentially, casting it as if the cleric was casting it, or treating the stolen spell as if it had come from a spontaneous caster such as a sorcerer. It sounds silly, really, but it's going to end up defining what I choose for my spontaneous domain casting, and what spells I need to have prepared.