Xur is located on Nessus in the Watcher’s Grove.
He has the following:
He’s selling gear with 270 Power, with Merciless for 29 Legendary Shards, and Raiden Flux, Wings of Sacred Dawn, and Doom Fang Pauldrons for 23 Legendary Shards.
If nothing else, pick up Merciless!
It’s a quite-solid straight up vertical buff to your Super. While I would argue previously that this ability is best relegated to trash clearance (orange bars are fair game, too!), this gives you the ability to chain together an increasingly damaging combo on bulkier foes. Providing they don’t have an anti-melee pushback or a too-damaging stomp attack, you can actually make yourself valuable in burn phases. A friend ran this in this week’s Nightfall and made short work of the final boss during the Arc phase. However, because Supers (and indeed, all abilities) recharge much slower in this game, for the majority of the time this Exotic is dead weight. In spite of this, it is extremely PvE friendly for a subclass that is otherwise arguably outclassed in endgame content by Nightstalker/Gunslinger. High A tier.
As /u/Jonesy2700 pointed out, you can work in a powerful stun-lock routine with the added damage on heavy strikes!
Doom Fang Pauldron
These are fun. While I personally can’t stand the look (my clan thinks I’m insane for this), they effectively give you the ability to throw as many shields as you want during your Super. Anyone who has toyed around with the Sentinel’s Void Captain America frenzy knows just how powerful and useful these ranged attacks can be. They can slice through multiple enemies, bounce around corners, and turn an otherwise fairly rote roaming Super into an unpredictable nightmare for enemies at all ranges. You might think they synergize especially well with the Code of the Aggressor, I would actually argue they’re equally (if not more) useful for the Code of the Protector.
There are plenty of times Ward of Dawn is unideal, and these give you offensive flexibility without needing to spec into Aggressor. If you still prefer Aggressor (and with Shield Charge, it’s hard to blame you), try to get your hands on Mask of the Quiet One, which works beautifully with Two Shields and make the Pauldrons redundant. Because of their ability to elevate Protectors to be real offensive threats, and the overall cool factor, low A tier seems appropriate.
Wings of Sacred Dawn
Be a butterfly of death. Have the high ground forever and for always. Get caught in doors. All this and more with the Wings of Sacred Dawn. Attunement of Sky fans will greatly appreciate the assistance in maintaining their glide for peak ability recharge time. Because of the natural reduction in accuracy while moving through the air and firing, the ability to hover without momentum allows for precise kills with lower impact weapons like Auto and Pulse Rifles, and more unwieldy long range weapons like Scouts.
Unfortunately, you expose yourself to all manner of incoming fire, abilities, etc. To this end, I would argue this Exotic has a higher skill ceiling. You need to know how to position, when to bunny hop, and when to float high above the battlefield. If you can take all these into account, you’ve got an Exotic that pairs exceptionally well with the Attunement of Sky. Just be extremely careful in harder content… and around jet turbines.