The Festering Desire is a free Sword that you can get during the Chalk Prince and the Dragon event in Genshin Impact. Over the course of the event, you can refine it to make it stronger. This will happen in two stages and are tied to sub-events that need to become active over the course of the main event.
Refining Festering Desire to level 2 is part of Act 2 of the event and will involve some grinding of that Act’s main activity.
How to refine Festering Desire to Level 2
To refine Festering Desire to level 2 you will need to play through some of the Ley Line Disorders that will appear in Dragonspine after Act 2 begins. These will be marked on the map by a red icon, and are a pretty simple concept.