During the mission “Cold embers”(or Cold ashes maybe) of the new DLC, when I need to secretly peeking the ritual of fire giants, I was found and the ritual was cancelled, then I shoot the leader, called Calder, to death. I know I shouldn't do it but I did. Now, because of the death of the leader Calder, the ritual never resume or restart on every night, so my mission stuck here.
Hope someone could fix this bug by putting this Calder back and thus restart the ritual, really thanks.