The awoken queen Mora Sav and Eris Morn are working together for what we don't yet know. It is all understandable from the cutscenes from TTK. The opening Mora Sav say "it was all part of the plan, the awoken have played they're part, now it's up to you my Hidden froend" Hidden has a capital letters as it in the name of a group run by Ikora Ray the warlock vanguard which Eris Morn joined. Clearly the Queen is speaking to Eris Morn. In the end clip Eris says "you were right my Queen they were the key" referring to us the guardians. We played a part without knowing. Killing the taken king was the first step in whatever they were/ are planning together. This next part is only rumors and theories however I have read several articles suggesting Destiny 2 will include Eris Morn and Mora Sav's plan and also link in the Nine as they have a lot to do with Mora Sav that's a different topic. Read the grimiours everything is in there you need if you want to learn plenty of the back stories.