Lightning Returns: Final Fantasy XIII shields

In Lightning Returns: Final Fantasy XIII, Lightning will have a variety of shields in her arsenal to be used. Their common traits are raising maximum HP and status resistance.

Shields can be upgraded from the second playthrough onwards after defeating the final boss. They can be upgraded at forges for a small fee and various materials that can be bought at the Adventuring Essentials, or obtained from defeated enemies. The best materials are only available as enemy drops.

It's not possible to upgrade shields to their maximum values because each item can only be upgraded a set number of times. One can max-out a couple of stats at most, but never all of the possible parameters. Upgrading a shield the first time earns the Novice Shieldsmith achievement. Upgrading a shield thirty times earns the Expert Shieldsmith achievement.

One can also downgrade shields, but this will not refund the materials used to upgrade them although it does "refund" the number of upgrades. Downgrading can therefore be considered as the backup plan in case one upgrades a shield the wrong way.

Guard Efficiency
Guard Efficiency is a percent damage reduction multiplied by the Physical and Magic Resistance of the used ability.

For example, with 100 damage the formula for receiving it using the example above would be:
 * $$0.75*0.85*100=ca.64$$

Instead of receiving 100 damage, Lightning would receive 64 damage.

Guard Defense
Guard Defense is a flat damage reduction which is calculated as a subtraction from the multiplication of incoming damage, ability's percent damage reduction, and a shield's Guard Efficiency.

Using the example above, the damage calculation for Guard Defense with 50 points would be:
 * $$64-50=14$$

Well-Balanced Shields
Well-balanced shields generally boost HP and Guard Defense.

Large Shields
Large shields boost HP and Guard Defense, but come with the drawback of reducing ATB Speed. They focus on providing massive amounts of HP and include the Auto-Ability Defender which increases Keep in order to reduce enemy interruption of Abilities.

Tactical Shields
Tactical shields boost HP, ATB Speed, and Guard Defense.

Ensorcelled Shields
Ensorcelled shields boost ATB Speed, Guard Defense, and Magic.

Light Shields
Light shields boost HP and ATB Speed. They focus on ATB Speed and include the Auto-Ability Guard Efficiency, which increases damage resistance by a certain percent while actively guarding.

Valuable Shields
Valuable shields boost HP and improve elemental resistance while guarding, but they reduce ATB Speed. They include two Auto-Abilities which strengthen elemental resistances.

Crest Shields
Crest shields boost HP and Guard Defense and have varying effects on ATB Speed.

Other Shields
The following shields are available either from having save data from previous entries of Final Fantasy XIII trilogy games or from downloadable content. Many of them have traits which are reminiscent of one of the seven types from above.

Gauntlets
Gauntlets are similar to ensorcelled shields in that they raise ATB Speed and Guard Defense by a fair amount, but instead of Magic they augment Strength. They are best suited for Schema which rely on physical abilities.

Trivia

 * All of the Large Shields are inspired by Arthurian Legends; Prytwen was the name of King Arthur's ship, Pendragon was King Arthur's surname, Dame du Lac, is French for Lady of the Lake, from whom he received Excalibur; Guard of Avalon, the paradise Arthur went to upon his death, and Knight's Pledge references the Knights of the Round Table.
 * The Riot Shield is not usable by Lara Croft in the 2013 reboot of , though this is implied by its description (Lara being "the Adventurer"). Rather it is used several times by enemies trying to kill her, most notably by a boss guarding the Radio Tower.