Brittle Bones

you are magically gifted causing some immunity, taking half damage from fire, ice, and thunder spells, however you trade your physical strength and can no longer withstand blows from physical objects. when damage is received from a physical blow (sword, arrow, dagger, knife, fists, or objects) you are immediately forced prone and have to succeed on a dexterity saving throw of 14 minus your dex modifier to have the ability to stand on your next turn.