The Elder Scrolls Online: Tamriel Unlimited

In the room right before the last boss with a calendar and locks with cells, you need to activate the calendar, it will show a symbol, then you need to find a lock with the same symbol and open this cell, and so on until you open everything. If you screw up, there will be an animation of the cell being doused with lava. As soon as you use the mods and open all the cells, the achievement will appear.