Potency (history)

Efficacy and Potency items work as "Universal" spell damage amplification and will work on spells with unusual damage types.
 * Blade Barrier - slashing
 * Cometfall - bludgeoning
 * Ice Storm - half cold, half bludgeoning
 * Flame Strike - half fire, half divine
 * Disintegrate - untyped
 * etc.