History of Armor Classed

Armor Classed is a triumph worth 25 Triumph score from Season of the Wish: acquire a full set of Season of the Wish armor. The seasonal set is the Wyrmguard armor (Mask/Grips/Tunic/Strides/Cloak for Hunters, with equivalents for Titans and Warlocks).

How to complete

1. Play the seasonal activities Riven's Lair and The Coil, which drop Wyrmguard pieces.
2. Open Wish Engrams at Spirit's Anchor with Riven, the seasonal vendor, and focus toward armor pieces; pieces also appear on the Season Pass track.
3. Collect all five pieces (head, arms, chest, legs, class item) for the class you are playing. The set carries the Ascendant Protector perk, which boosts Riven reputation gain.

Notes

This was a Season of the Wish (Season 23) triumph and is now legacy content. The sources I opened describe how the armor is obtained but not the triumph itself, so whether pieces for all three classes are required is unconfirmed; the description says 'a full set'.