Before you begin make sure that you have one mark of Chivalry
Go to 'The Eagle Market' (You can hunt the Earl to find it) BOW STATUE.
Make sure you get the blessing then head straight to the next location, it is timed.
Go to Caerleon and in 'Red Dragon Inn' is a statue of a dragon, bow statue.
Go to 'The Top of Mount Snowdow' from Snowdonia it is SWNNU, there you will find a Celt.
Buy the essence you require:
dragon - dexterity/constitution
hydra - perception/dexterity
wyvern - mind/spirit
Go to Camelot, give essence Merlin. It does not need to be the Merlin under the moat.