YIN SHIELD:

+1AC Resistance to melee attacks. When a friendly creature within 10ft of you is targeted for a melee attack: You can use a reaction to move to the creature and become the target of the attack. This skill can not be used when the shield is unequipped.

YANG SHIELD:

+1AC Resistance to ranged attacks. When a friendly creature within 10ft of you is targeted for a ranged attack: you become the target instead. This effect ends when the shield is unequipped.

YIN & YANG SHIELD (attuned version):

+5AC Absorbs the effects of both shields. Two-Handed. Cannot be unequipped while the shields are attached. You must make a STR check of DC 15 to separate the shields. The shield also grants advantage on saving throws against spells that do physical damage.

Shield of Harmony: Once every long rest, when a creature declares an attack on you: You can completely neutralize the attack and avoid all status effects that would be dealt by that attack. Everyone within 5ft around is also not effected by the attack as well.

Electrical Revenge: If a creature misses you by5 below your AC or more, then the shield can use a number of charges to react with one of the three following spells.

One Charge: Shocking Grasp. Roll to hit with advantage and add your Con modifier to your roll. On a hit, a creature takes 1d8 lightning damage. The spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).

Three Charges: Lightning Bolt. Your attacker has disadvantage on the Dex saving throw, but all others caught up in the line do not. The DC is equal to your Con score. A stroke of lightning forming a line 100 feet long and 5 feet wide blasts out from you in the direction of your attacker. Each creature in the line must make a Dexterity saving throw. A creature takes 8d6 lightning damage on a failed save, or half as much damage on a successful one.

Six Charges: Chain Lightning. Your attacker has disadvantage on the Dex saving throw, but all others that you target do not. The DC is equal to your Con score. Your attacker must be your original target. Three bolts then leap from that target to as many as three other targets, each of which must be within 30 feet of the first target. A target can be a creature or an object and can be targeted by only one of the bolts. A target must make a Dexterity saving throw. The target takes 10d8 lightning damage on a failed save, or half as much damage on a successful one.

Twelve Charges: Lightning Wall. A shimmering, yellow plane of light forms a vertical opaque wall--up to 90 feet long, 30 feet high, and 1 inch thick--centered directly in between you and your attacker. The wall remains in place for 10 minutes. The wall consists of seven layers, each being bright yellow. When a creature attempts to reach into or pass through the wall, it does so one layer at a time through all the wall's layers. As it passes or reaches through each layer, the creature takes 10d6 lightning damage on a failed Dex save, or half as much damage on a successful one. Each layer can be destroyed by dealing at least 60 force damage to it.

Shields require the Utilize action to Don or Doff. You gain the Armor Class benefit of a Shield only if you have training with it.

Notes: Both shields need to be in possession and equipped. On top of this, the user needs to have a "good" alignment. Otherwise, the shield will take years to use to it's full potential.