Skeleton

Size: Medium
Type: Undead
Alignment: Lawful Evil
Armor Class: 13 (leather armor)
Hit Points: 13 (2d8 + 4)
Speed: 30 ft.
STR: 10 (+0)
DEX: 14 (+2)
CON: 15 (+2)
INT: 6 (-2)
WIS: 8 (-1)
CHA: 5 (-3)
Damage Immunities: Poison
Condition Immunities: Exhaustion, Poisoned
Senses: Darkvision 60 ft., passive Perception 9
Languages: Understands the languages it knew in life, but cannot speak.
Challenge: 1/4 (50 XP)
Actions:
Club: Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 2 (1d4) bludgeoning damage.
Short Bow: Ranged Weapon Attack: +4 to hit, range 80/320 ft., one target. Hit: 5 (1d6 + 2) piercing damage.

Variants for your Skeleton (with Mace and Shield):

Since your skeleton has a mace and shield, we can slightly adjust its actions and Armor Class:

Skeleton with Mace and Shield

Armor Class: 15 (leather armor, shield)
Actions:
Mace: Melee Weapon Attack: +2 to hit, reach 5 ft., one target. Hit: 3 (1d6) bludgeoning damage.

Encounter Considerations:

Number: Skeletons rarely travel alone. A group of 2-4 skeletons can be a suitable challenge for a party of low-level adventurers. Commander: Skeletons often serve a more powerful master, such as a necromancer, lich, or vampire. This master might give them orders or even be present at the encounter.
Traps: Skeletons are often used as guardians of tombs or ancient ruins and might be strategically placed to ambush intruders or protect areas with traps.
Weaknesses: Remember, they are undead. They are vulnerable to radiant damage and certain spells that affect undead (such as "Hallow Ground").

This mace-and-shield-wielding skeleton is a basic but effective undead warrior.