Shield points, usually shortened to SP, is a measure of a character's defence. They reduce the damage done by most forms of attack, whether physical or magical, by one point of damage per shield point. They are usually granted by a character's equipped shield or artifacts.
The shield points of a shield can be increased by a blacksmith, at a cost equal to the final shield points multiplied by ten for each point the shield's shield points are increased by. The shield points of the shield can be increased multiple times at once, but the full price of all the upgrades must be paid.
Shields can also be Mythrilized or Adamantized by a blacksmith, which increases their shield points by 10 or 25 points, at a cost of 100 or 250 gold. Mythril or Adamantium Ore is required for this service. A Mythril shield cannot be Adamntized, and an Adamantium shield cannot be Mythrilized.
Artifacts cannot be upgraded in the same way as shields, however consumable items such as Bright polish can be used to increase a shield's shield points by one point, and can also be used on an artifact, provided the artifact already has some amount of shield points.