Upon the surface of a wall, door, or other non-living structure, you inscribe a rune, which illuminates cracks in the surface and creates an outline resembling a door. Upon snapping your fingers, the rune explodes, vaporizing the matter inside the outline and leaving a corridor. The mass of whatever structure was there is ejected away from you, in a straight line down this newly formed tunnel.   You touch the space you wish to place the rune as an Action, and then determine the size of the corridor. The corridor can be up to 20 feet long, 5 feet wide, and 10 feet tall, and will always be pointing inwards into the structure. Against magically-created barriers, the distance is halved. The corridor is stable and cannot collapse as the rune consumed the mass to form a safe tunnel. The Breaching Sigil cannot be applied to any living or undead structure, nor can it be applied to thin air.   You then detonate the Sigil as a Bonus Action. If the wall, door, or other non-organic structure is smaller than the dimensions of the corridor, the excess space becomes a blast zone.   Any targets caught inside the blast zone must make a Dexterity saving throw against your Spellcasting DC. On a failed save, affected targets take 3d8 Thunder damage and are pushed up to 10 feet away in a straight line from where the sigil was placed and are knocked prone. Targets that succeeded on their saving throws only take half damage and are not pushed away or knocked prone. Constructs have disadvantage on their saving throw against the effects of the Breaching Sigil. Any targets that failed their saves and were not inside initiative are Stunned until the end of your next turn.