Crystal Fragments is a skill located in the Dark Magic (which can be found in the Sorcerer skill tree). Crystal Fragments is a morph of Crystal Shard.
Crystal Fragments deals the following types of damage: Magic Damage. Which means that it gets buffed by the following blue champion point trees: Elemental Expert, Elf Born, Master at Arms, Spell Erosion. Also the following red champion point trees protect against this skill: Elemental Defender, Iron Clad.
ESO Skillbook