Vex Portal

In Shadowkeep, Ikora Rey said that Vex Chassis Components were being used to build a Vex portal behind her, and construction began with the latest weekly reset.

The components are common-rarity drops from Vex enemies on the Moon, especially during the Vex Offensive and Vex Invasion events. Their only known use is Ikora's weekly challenge "An Arm and a Leg", which rewards Powerful Gear after you collect a set number of them. The challenge unlocks after you have completed the Vex Offensive at least once.

Because the components kept dropping after the challenge was done, a later use was speculated when Shadowkeep launched.