Desynthesis is a new crafting ability added in FFXIV: ARR Patch 2.3. Players can break down pre-existing items and raw crafting materials by Desynthesis.
As FFXIV player, you are required to reach at least level 30 to gain Desynthesis. And then you must complete the quest “Gone to Pieces” in Ul'dah.
Crafters have their own Desynthesis skill level. There are 100 levels for Desynthesis skills. Each Desynthesis skill has its own points. The point maximum of 300 applies to all classes combined. Thus, you should reasonably allocate the points based on your character in A Realm Reborn.
Desynthesis can be used break down different items to get some shorts or other materials for your crafting. You can break down furnishings and housing. And you even break down fish, or break down equipment to gain elemental crystals or shards
Successfully Using Desynthesis
Desynthesis skill level affects not only the chances of successfully breaking down an item but also the materials yielded if you succeed.