- I received the wrong keystone from the Great Vault
- I timed a +11 last week and got a +9 out of my vault
How the Great Vault calculates your keystone
Since patch 9.0.5, if you finish a Mythic keystone dungeon in time during the week, the next week’s Great Vault will contain a keystone of that same level.
For example, if your highest Mythic keystone completion during week one is a +15 that you completed in time, you will get another +15 keystone from the Great Vault to start week two. If you run that +15 during week two and fail to meet the timer, however, and complete no other +15 (or higher) Mythic Keystone dungeons the rest of week two, you will receive a +14 keystone from the Great Vault to start week three.
My Keystone is of a lower level than it should
If the Great Vault gave you keystone of the wrong level it is likely because you were awarded an old reward. The Great Vault saves any rewards you don't loot, and shows you the rewards in order from oldest to most recent. You can see if the rewards you're receiving are old from a message above the Collect button.
You can only have one keystone per week. This means that, if the Great Vault already gave you an older keystone, you cannot receive a second, newer keystone, even if the newer keystone is better.
For example: You timed a +5 Spires of Ascension a few weeks ago, but never looted your Great Vault reward. You timed a +10 De Other Side last week. You loot your Great Vault this week. First you'll receive your +5 loot and a +5 keystone. You can then open the Vault a second time to receive your +10 loot, but you will not receive a +10 keystone, because you already have a keystone.
Game Masters cannot change keystones.