Quilt served as a necromantic focus to boost Miranda's necromantic spellcasting during The Oracle Hunter. Granted, he was in a much happier mood back then.
Ever since the conclusion of Two Thief Or Not Two Thief, Quilt and Bumper had developed a steady, out-of-the-spotlight friendship. It was never explicitly stated in a "hey, we're hanging out now!" sort of way, but they were often seen in one another's company.
Even in the beginning, when Detective Quilt was busy "interrogating" Bumper...
...to watching Dominic tap dance past them as they spent time at a Charlie Brown-esque wall...
...to seeing the debut performance of Facebath together.
It was originally the quiet development of two supporting cast members becoming closer friends, but Dominic's vision reveals their friendship meant a lot to Quilt. And now that he's lost his buddy, he's pissed.
That's all from me for now.
Rock on, and have a nice weekend!