The key system is smaller than the item count suggests
Two hundred and fifty-seven entries in the item database belong to the chest and access key group, which is more than half of everything the game publishes and looks impossible until you see the pattern. There are 41 named areas. Each of them has six keys — a plain Key plus a Damaged, Worn, Fine, Exquisite and Sacred version of the same thing — and nine of them additionally have a Treasure Key, alongside one more Treasure Key for Sealed Grounds. Learn the 41 area names and you have learned the system; the grades are the same lock in different condition.
What the grades change is not published in a form worth quoting. The names imply a condition ladder and the game prices them differently, but the units behind that are not confirmed, so this site does not publish how many openings any grade is worth. What is safe to act on is that a Sacred Key and a Damaged Key for the same area open the same lock, so a cheap key is a real substitute when a good one is not in your stash.
The ten areas that carry a Treasure Key are Cobalt Grove, Demigod Coast, Drill Yard, Einherjar Ship Grave, Main Hall, Prison, Sealed Grounds, Sunset Fjord, Verdant Grounds and Witchery Woods. Those are the ones tied to the locked treasure chambers the developers expanded before launch, and they are the keys most worth holding onto.
Every key tells you where its lock is
The single most useful thing about this system is also the least advertised: read a key's own description and it names the area and usually the exact spot. The Treasure Key for Verdant Grounds points at a cellar on the south side of the Verdant Grounds in Hallowgrove. The Sacred Key for the Watchtower points at the ground floor of the Watchtower in Hallowgrove. The Prison keys point at the upper eastern area of Brandrgarde's Prison, and the Drill Yard keys at the lower levels of the Drill Yard, southwest of the Underground Prison.
That means you never need a community location list for a key you are holding. Open it in your inventory or on the item database, read the second half of the flavour text, and it tells you the building and often the floor or the side of it. The first half is atmosphere; the sentence that mentions a place name is the instruction.
It also means you can plan the reverse way round. If your route already goes past the Smeltery or the Ritual Vault, checking whether you own a key for it before you enter turns a walk-past into a stop worth making. Keys you own and never think about are the most common form of wasted stash space in this game.
Which map an area belongs to
Of the 41 keyed areas, 14 are named in Hallowgrove and 27 in Brandrgarde, which tells you where the key economy actually lives. The Hallowgrove list runs Abandoned Market (South), Ancestor Tower, Demigod Coast, Divine Anchor (West), Divine Retribution Ruins, Einherjar Ship Grave, Frostwind Path (East), North Dwellings, Pioneer Gates (West), Refugee Camp, Soul Beacon, Sunset Fjord, Verdant Grounds and Watchtower. Everything else — the Prison, the Drill Yards, the Forge, the Smeltery, the Abandoned Furnace, the Exile Pit, the two Brandrgarde Pathway lifts and the rest — sits in Brandrgarde.
Several of the Brandrgarde descriptions go further and say which half. The Ancient Array, the Maw of the Abyss, The Forge (West), the Smeltery, the Abandoned Furnace and Cobalt Grove are all described as northern; Witchery Woods (West), the Elder Tower, the Ritual Vault and the Bridge Outpost as southern. Since Brandrgarde publishes as two separate maps, that detail decides which of the two you need to queue for before a key is useful at all.
For a solo player this is the sharpest consequence of the trio gate. Two thirds of the named key areas sit on a map you cannot enter alone, so a solo stash fills with keys that are worth selling rather than carrying. The auction and vendor side of that decision is covered on the vendor catalogs page, and keys are tradable, so they are one of the few loot categories with an obvious answer when you cannot use them.
Key rooms on the map, and the filter that hides them
The published maps mark key rooms as landmarks: four possible positions on Hallowgrove and five on Brandrgarde South. Brandrgarde North publishes none, along with no resurrection points and no merchant markers, which is part of why that map is the least forgiving of the three. As with almost everything on the interactive map, these are possible positions and the match rules decide which of them appear in your run.
They are also easy to miss, because key rooms sit behind the Special rooms context filter rather than in the main treasure layer. If you have never opened the filter panel, you have never seen them. Turning that one context on while leaving Mission and Soul Hunt off gives you the cleanest possible picture of where a key you already own might be worth carrying.
The practical habit is to check key rooms before the run and not during it. A key room is a stationary, predictable stop, which is exactly the kind of place other players learn to watch, so it belongs in the route as a planned detour with an exit direction attached rather than as a detour you improvise.
Containers are not interchangeable
The treasure layer is enormous — 770 markers on Hallowgrove, 723 on Brandrgarde North, 597 on Brandrgarde South — and it is built from around forty named container types per map. The commonest are not the valuable ones. Civilian Chests lead on both Hallowgrove and Brandrgarde South at 94 possible positions each, with 72 more in the north; The Exiled, Withered Nests, Woodpiles, Iron Pots, Straw Dolls and Open Sacks fill out most of the rest.
The rarer names are where a detour pays. Gilded Chests publish five possible positions on Hallowgrove, ten on Brandrgarde South and one in the north; Nobleman's Chests four, one and five; Jewelry Boxes five, six and five; Copper Chests four, ten and two. Equipment Racks are worth knowing separately because their distribution is so uneven: 21 possible positions on Hallowgrove against 51 in the south and 36 in the north. Bone Urns are almost a Hallowgrove-only sight at eight positions, with a single one in the south.
Some container types only exist in one place. Both Brandrgarde maps carry small, medium and large ore piles that Hallowgrove does not have at all, and the north adds Forge Furnaces, Timber Chests and Thermal Vents. Hallowgrove answers with Spirit Jars, Silverleaf Nests, Silverbough Altars, Sacred Tree Sacs, Oath Chests, Shipwrecks and Woven Flasks. If you are farming for a specific forging material rather than for gear, the container list is the reason to prefer one map over another.
The named containers worth learning first
Three entries in the game's own map legend deserve separate attention. An Enriched Resource Zone is described as an area rich in resources containing extremely valuable treasures — an area, not a container, so it is a place to allocate time to rather than a thing to click. A Supply Chest is described as holding equipment and items useful in battle, which makes it the one container type worth opening even when your bag is full, because what it gives you may keep you alive to the exit. The Ancestor Tree entry states that Gifts of Fate appear in numbers nearby once the tree awakens; the Ancestor Tree itself is an announced mid-season Hallowgrove feature with no published date, but the Gift of Fate container already appears on all three maps, at 37 possible positions on Hallowgrove, 46 in the south and 44 in the north.
Loose loot is a separate layer again — 114 markers on Hallowgrove including 30 airdrop positions, 120 on Brandrgarde South and 96 in the north — and it is the layer most worth enabling on a materials run, because it is the fastest value per second of standing still.
The one habit that separates efficient players here is refusing to open containers on the way out. Every container is time spent stationary and, on Brandrgarde, time spent inside a collapsing safe zone. Opening on the way in and moving on the way out is the version of this that survives contact with other squads.
Before your next run
Sort your stash by key before you queue and ask two questions: which of these areas is on the map I am about to enter, and does my route pass it? Keys do not stack in your bag, so each one you bring costs a full inventory slot that could hold loot instead — carrying six speculative keys is carrying six fewer things out. Anything for the other map, or for an area you never visit, is stock to sell rather than storage to keep.
Then place the key room or chamber inside the route rather than beside it, with an exit direction already chosen; the reasoning for that is in route planning and exit timing. If you are working through Hallowgrove first, its container and key-room distribution is broken down in the Hallowgrove map guide.