History of Boon Modifiers

Boon Modifiers asks you to "Complete an activity with a Boon modifier active."

How to complete

1. Open an activity from the Portal or Ops screen and go to activity customization.
2. In the Boon and Event Modifiers section, enable at least one Boon (e.g. Elemental Surges, Class Healing, Grappler, Brawler, Full Throttle).
3. Finish the activity with the Boon still active.

Boons are beneficial player boosts; the other modifier categories are Banes (buff enemies) and Player Stakes. Boons were introduced with the customization system in Destiny 2: The Edge of Fate. Easiest: pick a Boon on a simple activity such as an Onslaught run.