Undead Fortitude. If damage reduces the zombie shield guardian to 0 hit points, it must make a Constitution saving throw with a DC of 4 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 3 hit points instead.

Multiattack. The zombie shielder can use its taunt ability. It then makes one weapon attack.

Shortsword. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit 6 (1d6 + 3) slashing damage.

Dagger. Melee/Ranged Weapon Attack: +3 to hit, reach 5ft., range 20/60 ft., one target. Hit 5 (1d4 + 3) piercing damage

Shield Slam (defensive stance only). Melee Weapon Attack: +3 to hit, reach 5ft., one target. Hit 5 (1d4 + 3) bludgeoning damage. The target must succeed on DC 14 constitution saving throw or be stunned until the end of their next turn.

Taunt (recharge 5-6). Thezombie shield guardian slams its sword against its shield and releases a battle cry. All creatures within 15 feet of the zombie shielder must succeed on a DC 14 wisdom saving throw or receive disadvantage on all attacks that aren't against the zombie shield guardian. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Defensive Stance. The zombie shield guardian enters a stance that gives it a +4 to AC, but gives it disadvantage on all weapon attacks except it's Shield Slam and decreases its movement speed by 10 feet. The zombie shield guardian can use a bonus action to leave its defensive stance.

Block. When a creature makes a successful melee or ranged attack roll against the zombie shield guardian, it can give itself +2 to its AC, potentially turning a hit into a miss, until the beginning of its next turn.