Opulent Keys are currently the best way to get some of the reprised Menagerie weapons in Destiny 2 so here is a quick guide on how to get as many as possible with the least time investment.
Destiny 2 reissued Menagerie weapons that can finally be used in endgame content and high-end PvE since they will not be under the sunset treatment. On top of that, getting five Resonant (red border) copies of a weapon and extracting their Resonance will let you craft it with the perks you desire.
Unfortunately, their sources are somewhat scarce until you upgrade the HELM enough and farming chests on Leviathan is the way to go. This guide will lead you through the process so you can do it as quickly as possible.
Take everything that helps your mobility as there will be a lot of running involved. That means any subclass abilities or passives that help you get from point A to point B quicker on top of the gear that does the same.
Here are a few examples:
- Titans: Shoulder charge, Dunemarchers or Peacekeepers
- Warlocks: Icarus Dash, Transversive Steps
- Hunters: Stompees, Frostees
Additionally, all classes can benefit from Lightweight Frame weapons and swords to increase their mid-air speed. In the case of the swords, the best choice is a sword with Eager Edge perk for a mid-air dash, if you have the 30th Anniversary content.
The last, but most important part, is the Wombo Detector on your Ghost. It will help you see chests from a fairly long distance and this is exactly what you need.
Load into Leviathan by choosing either Containment. This will send you into a session where people are already doing Nightmare Containment so it you might be better off looking for the Pools entrance without engaging the event.
If you notice it's already on Tier 3, join in on the fun, complete the event, loot the chest and invest 500 Vestiges for additional loot. Check the rest of the Castellum for any potential chests and once that's done, proceed to Pools.
Alternatively, you can go to Gardens first.
Once you're in either Gardens or pools, look for chests and Nightmares around the place. If you come across a group of Nightmares, kill them as some of them yield chests that can also drop Keys.
Typically, you can find at least two chests per area before proceeding to the next. Once you've cleaned it out, proceed to whichever area you didn't go to.
One important detail to remember is that you need to use the Opulent Key as soon as you get it. You can't hold two keys at once so any chests you open while you have a key in the inventory will be futile.