Sanctuary, The Moon

After defeating Zulmak, Instrument of Torment in the Pit of Heresy, the Guardian speaks to Eris Morn.

Eris Morn: Since last we spoke, your fireteam delved into the Moon's depths and disrupted their dark ritual. But there is still much we do not know. On what powers did the Hive seek to call? What does it have to do with the Pyramid? And what do the dread queens Savathûn and Xivu Arath think of this new shade of Darkness? Stay vigilant. If my sight is true, the Hive will attempt this ritual again. You must be there to stop them.