I would say that "Cloak of Shadows" (was suggested earlier) but it would better fit a thief/mage and it lacks the power that a cleric/thief requires. How about some "Divine Thievery" HLA or something. "Drawing on the power of his god, the Cleric/thief is able to enhance his thieiving abilitis for a short time." A few extra point in thieving abilities for a short time never hurt anyone. But of course, that wouldn't really do too much for the cleric side of a Cleric/Thief...Any ideas for cleric-thieves?
I was thinking something which adds x2 to backstab and stealth for a while, but Cleric/Thieves can't backstab beacuse the only weapons they can use are weapons thievs can't backstab with.

Any better ideas?