Relic weapons (see source document for plentiful links to references)

Relic weapons were added to the DMM version in May 2017. These are purchased from the shop with elemental relic fragments from Ragnarok Disasters (which appear to have been introduced one element at a time from January-August 2017). These weapons can only be equipped by the corresponding Soul, and variants are available for each element.

Each Soul has a choice of two weapons, which grant the following when equipped as primary:
Base weapon skill granting a 11-30% elemental attack or HP bonus to same-element characters based on skill level (one weapon of each type per Soul)
Unique weapon skill granting a static bonus to one active ability
Soul-specific Burst effect shared by both weapons

These weapons are best-in-class when equipped by the corresponding Soul, but are essentially useless as secondaries since the base weapon skill is only active when equipped as primary. Some of these weapons are game-changing, such as D’art’s Charles Blast, which buffs Sniper Shot to -30% ATK/DEF, creating new build possibilities for elements lacking debuffs (like Thunder).