Start: Speak to King Arthur in Camelot
Requirements: Level 20 Attack, completion of Merlin's Crystal quest, ability to defeat a level 146 giant knight.
Items needed: Excalibur (Merlin's Crystal), Camelot/Falador or amulet teleports recommended.
King Arthur will tell you to speak to that former crystal prisoner, the trusted wizard Merlin, who lives on the eastern room upstairs. Merlin will tell you to talk to the High Priest of Entrana, and Sir Galahad, who is living in a two story house on the outside western edge of McGrubor's Wood.
First deposit any armour and weapons before going to Entrana. When you go there, go to the church and talk to the high priest. He will not care about the grail. The nearby crone will tell you about the holy grail and where to find it. Talk to the high priest again. Next, go talk to Brother Galahad in the house west of McGrubor's Wood. Ask him about seeking an item from the realm of the fisher, and he will give you a holy table napkin. Go to the top floor of Draynor Manor and retrieve two magic whistles in the room next to Professor Oddenstein.
(Note: If you lose your whistle after completing the quest, you can retrieve another one from Legends Guild Store.)
Take Excalibur, magic whistles, and whatever items you'd need to comfortably fight a lvl-146 monster. Go to Brimhaven, and head northwest until you reach a square plot of stone with candles. Stand on this and blow a magic whistle. You are now teleported to the Fisher King Realm. To go further, you must kill the Black Knight Titan (lvl-146). The final blow must be struck with Excalibur in order to defeat him. Now talk to the Fisherman, then pick up the bell on the west side. Ring the bell, and you will be teleported into the castle. Talk to the Fisher King who will tell you about his son. Once you finished talking to him, blow your whistle to teleport out.
Return to Camelot where King Arthur will give you a magic golden feather. Head to the Goblin Village north of Falador and search the sacks in the western hut to find Sir Percival hiding out. Give him a magic whistle. Now return to Brimhaven with a magic whistle and return to the castle, where you will talk to the new King Percival. Go upstairs and grab the holy grail, and return to Camelot to speak to Arthur.
2 Quest Points
Defense Experience = ((Level + 1) * 300) x Custom Rate
Prayer Experience = ((Level + 1) * 250) x Custom Rate