In the kitchen, you will see a Black Knight Assasin leaving through the window. Examine the fish in the vicinity to RuneScape gold find it poisoned. Instead of throwing it away However, have Savant use her magic on it. It will be given to King Vallance and he'll go unconscious. It's not dead, it's unconscious. King Vallance was paralysed by the altered poison in the fish, and the Temple Knights have an excuse to take him away in order to try and remove the slug.
At the Temple Knight Base, ask for Commander Callon to examine King Vallance to see if you can find ways to eliminate the slug. He will say that thanks to the slugs and the Karamthalu that you brought them, they believe they've got a way of splicing the slug from the king. The King will be recovering and then you can ask him if he has the slug's memories. He talks about dreams of a sea cave. Savant will be provided with locations of the cave.
To get to the cave, visit the port in Ardougne and then talk to the man standing in front of a tiny sailing vessel. He's actually a Temple Knight, the codeword to use is "Dancing for things pl0x". He will lead you to a small stone in the ocean that is soaking wet.
There is a cave when you go to the west. You can go in, and you'll be in a maze similar to the Kennith's Concerns quest. When you are through you'll find that you are not able to go inside the lair. Therefore, your character may suggest going to Aggie in Draynor Village.
In Draynor In Draynor, talk to Aggie about the slugs and the way to appear to have yellow skin and hair that is white. To change the hair, you must visit a hairdresser in Falador to have it changed. For the skin, Aggie will make a paste from flour water, ashes, as well as a rare Jeunefish. To catch a Jeunefish then return to the rock using the slug lair and use a super-fishing explosive to OSRS buy gold fish for dead juvenile fish.