Re. alignment, and saying up front that I have always disliked the D&D alignment system, to me being evil should not necessarily mean such a companion will automatically leave the party just because the party as a whole is good. An evil-aligned person can and should still feel that they want to remain in the party if they feel the party is continuing to serve their interests, interests that include staying alive in a world that is hostile to you. The system is rather simplistic and superficial if all that it is is to say: if you're "good" and I'm "evil" then I'm outta' here. Peoples' motivations are always way more complex than that. And writing characters with complex, complicated, deep motivations *is* about the quality of the writing.
