Complex sentence: His first trial comes one a maiden offers a bed for the knights but refuses to let Lancelot to lay on it, in which it is then revealed to be a trap to kill the knights, but it does not faze Lancelot.
Split into simpler sentences: His first trial comes when a maiden offers a bed for the knights, but refuses to let Lancelot lay on it. It is then revealed to be a trap to kill the knights, but it does not faze Lancelot.