She needed stock of three items. An object of Iron, a piece of tree root, and a fragment of amberglow. She did not see fit to sell the essence of Sun Tzu until he finished that task. Once Connor completed the task he was able to buy it for a mere 250 gold coins. Connor didn't know how to open the essence, and was told to just remove the warrior from the horse. Connor then imbibed the essence, and with a release of magic he became more powerful.