What a Keystone is

A Keystone is a real item, but a restricted one — it’s not ordinary itemization and it doesn’t behave like one.

• It can only exist in the root of your main backpack or the root of your main bank box — never in a sub-container, on the ground, in a secure trade, on a vendor, or in anyone else’s inventory.
• Starting a run requires it specifically in your backpack root; a Keystone sitting in your bank can’t directly start a run.
• It’s Blessed — it never drops to your corpse on death, under any circumstance.
• Your backpack’s item-count limit temporarily increases by one slot while a Keystone physically occupies it, so carrying one never pushes anything else out.

Party requirements

• 3 to 5 players.
• The roster locks the instant the run starts — there is no late join under any circumstance, so get your full group together first.
• Difficulty scales to whatever size your party was at the start. If someone leaves mid-run, the dungeon does not get any easier.

Starting a run

The run opens at the level of the run owner’s Keystone — that’s whoever’s Keystone is consumed to start it. While the run is active, that Keystone physically leaves the owner’s backpack; it returns at the end, regardless of how the run finishes.

What happens to your Keystone level afterward

• Finish on time (mandatory bosses dead + Enemy Forces at 100%) → level +1.
• Finish late, or the run ends any other way without an on-time finish → level −1.

There’s no neutral outcome — every resolved run moves your Keystone’s level by exactly one step. Leaving early as the owner returns your Keystone immediately at −1 and makes you ineligible for that run’s rewards, but it does not end the run for the rest of your party — they can keep going and still collect currency and artifact rewards. See Completion & Rewards for the eligibility rules in full, and Important Player Tips for what happens if your whole party disconnects or wipes.

There’s no hard level cap today — Keystones can, in principle, keep climbing indefinitely. High-key difficulty beyond what’s been tuned so far is explicitly a watch item for the team, not a guarantee that very high levels are already well-balanced.