Most things aren't easy in the dark ages- magic included. Whether spells don't function well or even at all, most would dislike even a cleric using magic.
Spells Available: Use either the standard cleric spell list or the divinity's, but check for each spell to its degree of availability to a particular dark age cleric. Different dark age clerics might thus have different spell selections, limited in various ways. Rolling a 12 as a magical side-effect is the only way to restore such spells, and even then, it's not guaranteed (see Part I). Roll 1d8.