Cleanse the Barrows
Note: This quest can be done alongside the quest "Corra's Fury"
As you are going to enter Corra's house, you may see a man named Rael. He has a quest for you to cleanse the barrows where you came from. Offer to help him to begin this quest.
After transporting back here, the "Altar of the Blue" you saw when you started will now be used. Go to it and when you approach it, the Darkbringer will appear and challenge you with a riddle. The answer to the first riddle is "Sword". If you get an answer wrong, he will simply summon darklings for you to fight which aren't a challenge. Whichever option you do, be it correctly answer his riddle or fight darklings, the ember corresponding to the Altar will be dropped. Do this similar to the Hay bales you dragged and drag the ember on the shrine.
Go to the upper level and head to the closest one, the Altar of the Red.
Go ahead and approach it to trigger the Darkbringer's appearance again.
Again, he confronts you with a riddle. The answer to the second riddle is "Silence".
The next one is the "Altar of the Green.
The third riddle's answer is "Wind"
Head to the last shrine and answer "Blood" to his last riddle.
Upon placing the last ember, the task will be done.
Return to Rael to collect your reward.