Book: The Taken King.
“...and so that's the situation. With Cayde's help the Guardian has established a beachhead on the Dreadnaught. I'm caught in the impossible position of wanting to reward and punish them both. If you have any guidance in this matter, it would be appreciated. I'll file another report this evening. For now I need to go have another conversation with Eris Morn before she rends Cayde limb from limb.” - Commander Zavala, transmission to Traveler's Observatory