The Psion has given Lord Saladin the knowledge claimed from the mind of the Hive that you brought to the Psisorium.
The Lucent Hive appear to be hunting Guardians, draining them of their Light, and collecting it—storing it for later use. The Psion doesn't know why.
"Savathûn knows how to keep a secret," Saladin says, "and so do her Hive."
Saladin asks you to find another Hive Lieutenant and defeat it in the Mindscape. He hopes it will have the knowledge locked away in its mind that the Vanguard seeks.
"I need you to hunt more of them," he says. "Cut them off from their Light and make them wither in the face of ours."
"They hate us… they want to usurp us. Become us. I will never let that happen."