| less depending on your prayer level

Talk to King Arthur in Camelot Castle. He will task you with retrieving the Holy Grail and direct you to Merlin for more details.

Go upstairs to Merlin's lab and talk to him. He will tell you about Sir Galahad, who lives west of McGrubor's Woods.

Go to Brother Galahad's house west of McGrubor's Woods. He will explain that he found the grail once but left it out of respect.

Travel to Port Sarim and take a boat to Entrana Island. Ensure you have no weapons or armor equipped.

On Entrana, go to the church and speak with the High Priest. Express your interest in finding the Holy Grail. The Crone will interrupt and speak of the Fisher King, mentioning you must blow a whistle where all six heads point. Ask her about the whistle and how to obtain it.

Return to Brother Galahad and ask him for an item. He will give you a Holy Table Napkin.

Go to Draynor Manor (north of Draynor Village). Proceed to the top floor and the easternmost room. You must have the napkin in your inventory to see the magic whistle. Pick up two magic whistles, as you will need a second one later.

Prepare to fight the level 146 Black Knight Titan. It is recommended to have a Prayer level of 37 to use the 'Paralyze' prayer. Bring your Excalibur from the Merlin's Crystal quest; if you don't have it, you can obtain another from the Lady of the Lake. This weapon is required to finish off the knight.

Once prepared, travel to Brimhaven. Head west until you reach the poison scorpions. Step onto a small platform and blow the whistle to be teleported.

Head west and talk to the Black Knight Titan to initiate the fight. This is considered the hardest part of the quest.

After defeating the Titan, go around the fence to a small peninsula. Talk to the fisherman and ask how to enter the adjacent castle. He will instruct you to pick up and ring one of the bells.

A bell will appear on the side of the castle. Pick it up and ring it to be teleported inside.

Inside the castle, talk to the Fisher King. He will tell you about his missing son and his hope for his barren land to be restored upon his son's return.

Use the whistle to exit the castle and return to Camelot.

In Camelot, speak with King Arthur and ask about the Fisher King's son. He will give you a magical feather that will guide you.

For a faster approach, go to Goblin Village and enter the westernmost hut. Right-click on the sacks and 'prod' them. The Fisher King's son will appear. He will recount how he ended up there. Tell him his father wishes to speak with him, and then give him the whistle.

Return to the Fisher King's Castle. Talk to the Fisher King, who will express his joy at his son's return.

Go upstairs and then up the ladder to retrieve the Holy Grail.

Return to Camelot and speak with King Arthur to receive your reward.