The phrase "piece for: GHOSTRUNNER HEL PROJECT" likely refers to one of the following creative components from the DLC:
For visual inspiration or reference, several lead artists have shared official concept art "pieces" for the character and the DLC environments: GHOSTRUNNER HEL PROJECT
The official soundtrack for Ghostrunner: Project HEL was composed by . The EP consists of six tracks, any of which could be the "piece" you are looking for: Caution Tank Dynasty Flow Overdrive Horizon 2. Sword & Glove Pieces (Collectibles) The phrase "piece for: GHOSTRUNNER HEL PROJECT" likely