Armor of Wound

You  can choose no more than 2 creatures(can include yourself) within 30 FT affect by this spell, for the next 2 hours, during an encounter, when the creature affected by the spell loss Hit Points, they gain more AC according to their remaining hit points, if they lost hit point, they gain  +1 AC(total 1), if their hit points is below 1/2 of its max hit points, they gain another additional +1 AC(total 2), if their hit points is below 1/4 of its max hit points, they gain the last +1 AC(total 3). If their hit points  recovered, the effect will fade according to their remaining hit points,( for example, a creature's max hp is 32, its remaining hp is 15, the creature receive a healing spell and now its hp is 17, the effect will be +1 AC. )