Adaptive Barrier

You or a willing creature you touch gain a protective barrier which can absorb Incoming magical damage. The barrier has no effect until you take one of the following damage types from a magical source; Fire, Cold, Thunder, Lightning, Force, Necrotic, Radiant.

Upon taking one of the listed damage types, the barrier becomes tuned to it. Once tuned, the barrier absorbs and negates 2d6 of its tuned damage type.
Taking damage of a different type will cause the barrier to retune to that type. The barrier cannot retune in quick succession and will break if hit with two different damage types within the span of one round.