I found as a cleric when I soloed him (at level 5 or 6, been a while) that searing light was reasonably okay, as was nimbus of light. If you have the SP for it, suggest MM, then nimbus while MM is cooling down). Or MM/SG/nimbus. He hit so hard, if you arentable to range him, you're going to need to drop him as quicky as possible. potency/efficacy items work well for all of those spells.