Holy Grail

Go to the first floor using the staircase and talk to Merlin.

Go to Entrana by talking to a Monk of Entrana. You will be asked to bank armour and weapons, which can also be done at the bank deposit box at the docks.

Speak to the high priest, who is in the main chapel of the church.

Speak to the crone who appears.

Head to Seers' Village lodestone.

Talk to Galahad, located in a building west of McGrubor's Wood and east of the coal trucks.

You must speak to the crone on Entrana first, or he will not give you the holy table napkin.

Take the holy table napkin to the southern room of the top-most floor of Draynor Manor. The way to the topmost floor is by climbing the main staircase and using the ladder on the southern wall.

Pick up the two magic whistles on the table.

Go to Brimhaven and blow the whistle under the wooden watchtower (refer to the map on the right).

Go north-west and defeat Black Knight Titan with Excalibur. Low levels may find it useful to safespot the Black Knight Titan with Magic, Ranged, or Necromancy and last hit him with Excalibur.

Head south along the river and talk to the fisherman by the river.

Be sure to keep the magic whistle in your inventory from this point forward.

Go south-west, to the castle. Take the grail bell on the ground outside the castle and ring it.

Head upstairs using the south staircase and talk to the Fisher King.

Talk to King Arthur in Camelot Castle. Make sure you have space to receive the magic gold feather.

Teleport to the Falador lodestone.

Head north to the Goblin Village, go into the eastern house, and right-click to open the sacks to find Sir Percival.

Return to the Fisher King's castle in his realm by blowing your whistle north west of Brimhaven (or by using Fairy ring ).

Go up the staircase on the east side of the castle, climb to the top floor and grab the Holy grail.

Go back to King Arthur.

Quest complete!