Crystallized Skeleton

Undead Fortitude. If damage reduces the Skeleton to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the Skeleton drops to 1 hit point instead.

Magic Resistance. The Skeleton has advantage on saving throws against spells and other magical effects.

Crystalline Claws. Melee Weapon Attack: +3 to hit, reach 4 ft., one target. Hit: 5 (1d6 + 2) piercing damage.

Crystalline Bite. Melee Weapon Attack: +2 to hit, touch., one target. Hit: 2 (1d6) piercing damage. Causing light petrifying in the form of crystals to the wounded area lasting for 2 hours.

Sword. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 3) slashing damage.

Shatter. Upon death, the crystals explode outward within 10 ft. All within range must make a DC 10 Dexterity saving throw or take 3 (2d6) piercing damage.

Lightning Charge. Whenever the Skeleton is subjected to lightning damage, it takes no damage and instead has all its attacks now do lightning damage for 1 hour.