Grace is the supernatural essence of angels and is what allows them to use their abilities while on earth. Created, specifically, to actuate the abilities of angels while within vessels, they are rendered practically mortal without them. Given to them by God, it's what differentiates them from humans while on Earth in a human vessel. If lost, an angel loses his or her powers and is rendered mortal and becomes subject to human weaknesses, needs, and desires.
The power of it, with it being pure energy, can enrich its surroundings, making a seed grow into a large tree. . As pointed out, such is its power that it causes not pure destruction, rather pure creation.