Following the boss fight with the Beast, speak with the human knight who magically appears in the courtyard with you to receive yet another side-quest – to kill a Poison Beast in the Keystone Citadel.
Return back inside the Citadel and follow the main hall until you bump into the guard who appeared outside when we killed the Beast. Speak to him to start the next part of his side-quest. When you are done, head through the now unlocked door opposite his position. It’s the Initiation Room where we fought the Warden at the start of the game! This time however, there is a new baddie in his place.
Once you have killed the Poison Beast, loot the Sealed Rune (Small) he drops and then return to the quest giver and speak to him for another 7,500 XP.