The Lady also known as Lady of the Lake is an NPC featured in Merlin's Crystal and The Holy Grail. During Merlin's Crystal she appears in the disguise of a Beggar in Port Sarim outside of Grum's Gold Exchange, asking the player for bread to test if they are worthy to wield Excalibur.
The Beggar's test can be repeated in order to obtain multiple copies of Excalibur using the drop trick. This requires one bread for every copy of the sword obtained. It can be repeated after completion of the Merlin's Crystal and Holy Grail quests.