A Gray Matter

A Gray Matter is a hero quest in Xenoblade Chronicles 3. It can be received by heading for the quest marker at Murmur Rise in Millick Meadows. The Traversal Skill Wall Climbing, acquired by completing The Kind Right Hand, is required to reach it. Completing it will make Gray available as a Hero.

Result
"The mysterious man gave you his name: Gray. He also seemed to know that Noah and co. were Ouroboros, and ultimately offered them his help."

Trivia

 * On a NG+ file, Gray can already be unmasked during his hero quest. However, he will wear it during cutscenes and during fights, his model changing as the fight begins.