Parsifal
The opera starts with an orchestral prelude (Wagner does not call it an “overture”).  When the curtain rises Gurnemanz, one of the senior knights, wakes up two sleeping servants.  They kneel and pray as King Amfortas is brought down on his bed to the forest lake to bathe his wound.  Kundry arrives, dashing in on her horse, looking for something to heal the wound (when Kundry is away from Klingsor she is not in his power.  She feels that it was her fault that Amfortas was wounded.  When Kundry is not in Klingsor’s power she is actually a faithful messenger of the Grail).