This was from a green lockbox. I actually just found the Battlelord's gloves in a Jeweled Premium Mission Box today when I logged in. I know that blue items do occasionally drop out of green lockboxes, and since I think blue and custom are considered equal its not surprising to see the Battlelord's set dropping out of green lockboxes.
Nevertheless, that makes two pieces of Battlelord gear now I've found in lockboxes
Jedi Battlelord's Headgear - Black Market Premium Mission Case (TH 49-50)
Jedi Battlelord's Handgear - Jeweled Premium Mission Case (TH 41-48)
I actually did find the headpiece of this set for the first time in a Black Market Premium Lockbox today. I've found pieces of the Smuggler set before but this is the first actual Battlelord piece I've gotten (sadly I already have it T.T). But you can count this as confirmation that the pieces do come from the level 49-50 premium lockboxes.
Putting on the headpiece will remove the hood, but only if you have it set to show the headpiece. Unfortunately, the headpiece doesn't look too great, so I've just been sticking with the hood. XD Sooner or later I'm sure we'll get a hood toggle.
Been asking around about the greaves (since they're the only piece I've seen pop up on the AH so far) and word is they come from the level 50 daily lockboxes.
Where did this drop on Voss? Off of what enemy? I've been searching long and hard to try and figure out where this set comes from, but haven't been able to find any solid information so far.