Periodically gain a single use of another random keystone. Once a keystone is rolled, it can't be rolled again until only three options are left, at which point the table resets (you won't get the keystone you just used, though).
Gain a new keystone 8 − 4 (based on level) seconds after using the last (12 − 8 (based on level) seconds for ranged champions). Scaling is weighted toward later levels.
Gain a new keystone while out of combat after 40 seconds of not using a keystone.
Your current keystone shows up to the right of your health bar. All ten players can see it.
Dark Harvest souls persist after you get a different keystone and affect all your other keystones. Grasp of the Undying's health persists after you get a different keystone, too.
Predator is only available to champions who have already purchased boots. Dark Harvest souls amplify the effects of all keystones. Aftershock is only available to champions who have learned a basic spell that can trigger it.
Does not re-roll if in-combat.
Keystones cycle pseudo randomly - you cannot repeat a keystone for 5 rolls after it has been used.
Entering the fountain will reroll your current keystone.