It isn't 39d6. It is 7d6+6d6+...=39d6, which is very different when there is energy resistance at work.eamon said:Last tuesday my party of 7th level detonated a Necklace of fireballs type V while under the effect of energy resistance and despite the triggering fire effect of 2d8+16, and the detonation of 39d6 damage, they all survived - though the dragon they were hunting was less lucky (being left at exactly 1hp)
Energy resistance works wonders against simply blasting.