Mordenkainen's Tome of Foes, p. 126
False Appearance. While the stone defender remains motionless against an uneven earthen or stone surface, it is indistinguishable from that surface.
Magic Resistance. The stone defender has advantage on saving throws against spells and other magical effects.
Slam. Melee Weapon Attack: +6 1d20+6 to hit, reach 5 ft., one target. Hit: 11 (2d6+4) 2d6+4 bludgeoning damage, and if the target is Large or smaller, it is knocked prone.
Intercept Attack. In response to another creature within 5 feet of it being hit by an attack roll, the stone defender gives that creature a +5 bonus to its AC against that attack, potentially causing a miss. To use this ability, the stone defender must be able to see the creature and the attacker.