Bound. The guardian is magically bound to an amulet. As long as the guardian and its amulet are on the same plane of existence, the amulet's wearer can telepathically call the guardian to travel to it, and the guardian knows the distance and direction to the amulet.
Regeneration. The guardian regains 10 hit points at the start of its turn if it has at least 1 hit point.
Improved Critical. Attack rolls score a critical hit on a roll of 19 or 20 on the d20.
Extra Attack. Can attack twice instead of once whenever it takes the Attack action on its turn. If the creature has the Multiattack action, it can use Extra Attack or Multiattack on a turn, not both.
Battle Readiness. Has advantage on all initiative rolls.
Improved Defense. Armor Class increases by 1.
Indomitable. Can reroll a saving throw that it fails, but it must use the new roll. When it uses this feature, it can't use the feature again until it finishes a long rest. Can use this feature twice starting at 18th level.
Multiattack. The guardian makes two fist attacks.
Fist. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 5) bludgeoning damage.
Second Wind. Can use a bonus action on its turn to regain hit points equal to 1d10 + its level. Once it uses this feature, it must finish a long or short rest before it can use it again. Can use this feature twice between rests starting at 20th level.
Shield. When a creature makes an attack against the wearer of the guardian's amulet, the guardian grants a +2 bonus to the wearer's AC if the guardian is within 5 feet of the wearer.