Tainted Blood is a quest that is part of the joining ritual of the Grey Wardens. You have to gather three flasks of Darkspawn blood to complete it.
In order to join the Wardens, you need to drink darkspawn blood, which Duncan wants you to find in the wilds.
- Leave Ostagar and enter the Korcari Wilds.
- As you progress through the area, you should run across several Genlocks and Hurlocks. Just search their bodies for the blood.
- Once you have also found The Grey Wardens' Cache, return to Ostagar.
- Remember to talk to the Kennel Master to turn in the wilds flower as part of The Mabari Hound quest.
- You can now pick up Codex Entry: Dogs in Ferelden from a Note in one of the empty kennels.
- You can purchase a second Backpack from the Quartermaster (and pickpocket a second Hardy's Belt from him).
- You can now pickpocket Duncan again to get single valuable item or some money.
- The tranquil mage has now moved from by the chest, so you can complete The Hungry Deserter side quest.
- Before talking to Duncan and beginning the joining, you can strip Daveth and Jory of their weapons and armor and sell it, but if you do not then their equipment will appear in your inventory after the Joining ritual. Note that if you do strip him, Jory will still appear to have a sword during the subsequent cutscene.
- If you have also found The Grey Wardens' Cache, you are now ready for the Joining ritual.
- You, Daveth and Jory will now be taken to the ruined temple where you first met Alistair and put through the Joining.
- You will be rewarded with EXP and an additional spell or talent.
- Duncan will ask you to follow him to meet with King Cailan, and you will receive the quest After the Joining.
- See Exploits for information about an infinite experience bug in some versions of the game.