Did that quest on the notice board, something about a "scouting party". Had to escort Mercedes there. Welp, we encountered some larger monster and because she is bad at fighting, she died and the quest failed. Redoing it is not possible, right? At least I didn't see it anymore on the board and it's marked as "failed" on the list. Is Mercedes permanently dead though?

Quest is going to remain failed until next playthrough.

Mercedes should be back to life in maximum 7 days of in-game time.

Oh well, reward wasn't that good anyway.

Good to know, thank you.