Iseldir

"You meddle with a power you do not understand, Arthur Pendragon. By taking the Cup of Life, you risk more than you know."

- Iseldir

Iseldir is a Druid chieftain.

When Arthur returned Mordred to his kind, Iseldir thanked him and declared the druids to be forever indebted to the prince for the kindness he had shown them. (The Beginning of the End)

After Merlin killed Nimueh, the Cup of Life fell from her possession to Iseldir's for an unknown reason. He now led a group of Druids inside Cenred, near the border to Camelot, his group Druids looked for survivors among fallen soldiers from Camelot after they were slaughtered on Cenred's orders. Sir Leon was the only one they could save. Iseldir used The Cup of Life to restore Sir Leon back to health.

Uther Pendragon sent Arthur on a quest to take the Cup from the Druids and have it stored in the Vaults of Camelot. Once Arthur found the Druids, Iseldir handed him the Cup but warned him of the powers he's dealing with. As Arthur left, he telepathically contacted Merlin, referring to him by his name by the Druids, Emrys, informing him that he was now the Cup's caretaker. (The Coming of Arthur)