Killing Chalier in Clair Obscur Expedition 33 is an optional objective you'll come across in the game's Floating Cemetery region.

Expedition 33 might be the most fun I’ve had playing a role-playing game since 2023’s Baldur’s Gate 3. Its turn-based combat ...

Clair Obscur has its fair share of weird and ... then head left and descend the rope until you reach a Mime flanked by two Obscur Nevrons. Location: Past the Ladder Area fast travel point.