As someone whose main role-playing outlet is DMing D&D 4e, I found Kobold Quarterly 21 to be a bit thin on good material. As someone whose day job is on a university’s religion faculty, I was fascinated by the varied treatments of divine magic in this issue and the varied ways of translating ideas about divine magic and faith into game mechanics.
Although “Daughters of Lilith: Ecology of the Succubus” is marked as a 4e article, it’s mostly free of game mechanics—and thus equally appropriate for any fantasy RPG that includes succubi—until the very end. Zeb Cook’s article on mystery religions is completely systemless, and very useful. Tim and Eileen Connors’ article on “Clerical Conflicts” employs a lot of Pathfinder crunch, but has a lot of story elements too that could easily be ported over to 4e or other systems. Steve Winter’s column asks “Why No Monotheism?” is pretty short, and actually spends more time answering the titular question than providing any hints for GMs wishing to run monotheistic settings (the advice occupies basically the final column of the two-page article). I enjoyed the interview with Bill Slavicsek. The “Scriveners of Allain” article, though 4e in mechanics, didn’t light my fire; the Pathfinder article presenting the witch louse was much more engaging (though somewhat disgusting).
Kobold Quarterly is always a mixed bag, unless you play several different game systems or are willing to put in the extra work to convert other crunch to your favorite system. If you’re strictly looking for material for just one system, I’d say this issue is worthwhile for Pathfinder, less so for 4e. If you’re up for mining articles written for a different system than the one you usually play or run, KQ 21 is a worthy entry in the series.