Hey Ryan, like Kent said - you can get it from treasure of ages but you'd be better off trying to get it from [i]sterling treasure[/i] which can be obtained once a week from prison of elders. [spoiler]Treasure of ages has more rewards so it'd be less likely to drop desolate armour compared to sterling treasure.[/spoiler] I'm not 100% sure on this but I believe you have to do prison of elders first before the other weekly activities, if you do the other weekly activities first then it'll remove the sterling treasure as a reward. Hope this helps! :)

Yes, you need 'Treasures of Ages' boxes, it can be found in weekly story, strike missions, crucible.. or buy it from Tess Everis)