Speak to Ikora in the Tower about the latest developments in her plan to destroy the newly resurrected Undying Mind.
Ikora wishes you a happy Festival of the Lost and apprises you of her progress on the Vex portal, where construction is proceeding as planned. But there's more work to be done before the portal can be put to use.
Enjoy the Festival of the Lost while Ikora continues work on the Vex portal.