Mountain's Root Armor

As a reaction at anytime, once per long rest, you
may increase your mass. Until the end of your
next turn, you may ignore any forced movement,
you have resistance to non-magical bludgeoning,
piercing, and slashing damage, and your speed is
a maximum of 15 feet.
Forged from rare materials found deep inside the
Star Mounts, the wearer of this impenetrable armor
cannot be forced back by any means.