Hmmm... according to the Neverwinter Nights manual, there is supposed to be a 5th level Cleric spell called Summon Shadow. For whatever reason, my cleric does not have access to the spell. Either a) there is some sort of prerequisite to getting access to the spell or b) BioWare simply didn't add the spell to the game. Until I find out, I have removed Summon Shadow from our fifth level cleric spells. Thanks to Jani for the heads up.