Doing so before the timer runs out will earn you powerful gear that scales depending on what Mythic Plus level the dungeon is. Mythic Plus dungeons are timed and in order to beat one you must also kill a certain number of regular monsters in addition to the dungeon bosses.Many of them require specific strategies to survive.
Some make monsters explode on death, while others increase the heath of boss monsters.
This Keystone opens a single Mythic Plus dungeon at a specific level, and completing that dungeon will transform the Keystone into a different one while also increasing the level. Dungeons start at +2 and scales infinitely, increasing monster health and damage.
