Crystals of the Imperium is a side quest in Dragon Age: Origins - Awakening.
You receive the quest automatically after entering Drake's Fall.
You need to find 12 crystals through the area, and with them, "turn on" the old Tevinter Towers. There are 3 of these towers in Drake's Fall (check the marks on your map), each one of them has four Sockets where you can put the crystals you found along the way. Once turned on, each tower enables a special power (shown on the icons on the right side of the screen) that can be used in your battle against the Mother. Since the area has a single way to go, it's fairly easy to find all of the crystals.
The 12 crystals are listed in order of appearance:
1st - Automatically received upon entering Drake's Fall.
2nd - Right after entering the area, on the right there's a small area and a locked chest with the crystal.
3rd - Looted from the Armored ogre after the stairs of the first Tevinter Tower.
4th - Also after the stairs of the first tower, it can be found in a Flesh Pod either by the staircase, or in the little room where the ogre came from.
5th - In the small area outside the tower, you can find it in the Flesh Pod, next to the 4th.
7th - In the same hallway, you will loot it from the Disciple Alpha.
8th - In the second Tevinter Tower, after the cutscene with the Architect, there's a crystal in the Flesh Pod in the surroundings.
9th - In another Flesh Pod almost at the same place as the 8th crystal.
10th - In a Flesh Pod, in the hallway to the third Tevinter Tower, close to the entrance of it.
11th - Found at a Flesh Pod after going down the stairs of the third tower, where you face Childer and a Heretic Disciple.
12th - At a locked chest close to where you find the 11th crystal.
If you follow the locations above, you will always have at least 4 crystals before leaving one tower, making it possible to activate the tower right away, or you can collect them all and then go back to activate all 3 towers at one time. The sockets are located at the ground of every tower (hit TAB if you're having trouble finding it, or look at the picture). After you fill the four sockets, the tower will unlock its power. Do it with all 3 Tevinter Towers to complete the quest.
Activates the following Tevinter Towers to be used in the battle against the Mother:
Tower of Healing
Both heals and resurrects (if dead) your party members.
Tower of Trauma
Stuns the enemies for a short time.
Tower of Flame
Lights a specific/targeted enemy on fire.
Tower of Pyre
Summons Fire in a designated area. (Friendly fire possible)