Ok so I you look behind them they are in the House of Winters lair. Notice that little balcony where hobgoblins spawn for archon mission. Definitely not a raid for that reason. I doubt that's prison because prison of elders lore says it's in the reef so it can't be that. Obviously not trials of Osiris because that's on Mercury. Belly of the beast (new strike) is on the moon, so not that. It's either for a mission, or a weapon usable for all content. I studied lol XD