Carnage Unity is one of the systems featured in Tokyo Mirage Sessions ♯FE. Carnage Unity consists of using materials earned in battles or found in dungeons to create new weapons called Carnages for Mirages to wield. Equipping these weapons allows the Mirages to learn skills or power up skills that they have already learned.
Stronger Carnages can also have influence over a Mirage's elemental affinity chart, more often than not giving additional weaknesses while at the same time switching around resistances or neutralities, eventually adding nullifications, repels, and drains. Passive Skills that influence defensive affinities do not influence how a Carnage's affinity chart is displayed in the Carnage Unity menu.
Following the conclusion of The Next Generation, using this service after Class Change becomes available will unlock new Carnages tied to that class, typically three at a time. Note that once a Mirage has been promoted into an advanced class, those specific Carnage Unity recipes remain unlocked even if a Mirage is re-classed. For example, Chrom can be promoted to Great Lord and then reclassed into Conqueror to unlock all six of his promotion-exclusive Carnages.
Later in the game, the ability to perform Carnage Unity on a Carnage that has already been created is unlocked. Doing so gives the Carnage a slight boost to its attack power and allows the Mirage to relearn and power up the skills associated with it, and to learn an additional fifth skill that was not available at the Carnage's base level. It does not require material components to reforge an existing Carnage, but on rare occasions, a Carnage the player selects to reforge may shine, indicating that Tiki can power it up even more by spending additional Performa.
In New Game+, the ultimate Carnage of every party member can be crafted after earning the Performa War Testament, obtained after completing the Legendary Arena circuit in Illusory Urahara.