An augment crystal is a small gem, crystal, or similar object that provides a magical effect when affixed to an item. Each item can hold a single augment crystal, but an attached crystal can be swapped for another one at any time. Attaching an augment crystal to (or removing it from) an item requires a move action that doesn’t provoke attacks of opportunity. Effectively, each eligible item has a single “slot” that can be filled by any appropriate augment crystal.

Crystals can come in 3 forms, Least, Lesser and Greater. You must meet the level of a crystal to be able to use it.

Crystals fall into 1 of 2 categories, either Armor Augments or Weapon Augments.

Image – https://www.proprofs.com/quiz-school/story.php?title=what-gem-are-you_536