The Spirit will obey you and grant you your wish in the game

Now to get the magic words, head to Varrock, South of the Rune shop in Varrock is a prayer altar. Check the Last Chaos Gold altar to get a message.

Once you have done the 4 requirements, head under the patio northeast of

Camelot Castle (there should be a water source icon on the mini-map at where the patio is). Go to the center of the red circle that is underneath the shelter and drop your bat-bone.

A level 92 Spirit will appear. Choose the option “Snarthon Candtrick Termanto” when it asks you to cite the magical words. Make a wish to free Merlin. The Spirit will obey you and grant you your wish.

Head back inside Camelot Castle. Open the 2 set of doors on the southeast corner and head up the 2 set of ladders. Use your Excalibur sword on the giant crystal to smash Merlin free. Merlin will give you many thanks for your help.

Attempt to open the door. A beggar will then appear beside you and ask for a piece of bread. Hand her one. The beggar will then transform back into her original form of Lady of the Lake and hand you the sword, Excalibur.