Friends in Low Places
This quest becomes available once you have completed at least half of the quests of Act 1. Go to Gamlen's house, read the letter on your writing desk, and accept the quest. This quest is an alternative to raising the 50 Sovereigns needed to pay Bartrand. If you realize you cannot raise enough money (maybe you spent too much on equipment) then this quest is your only way to advance to the next act. If you do have 50 Sovereigns available, it is recommended you do not do the quest and instead skip directly to The Deep Roads Expedition Quest. Doing Friends in Low Places instead of paying the 50 sovereign will reduce your profits from the Deep Roads Expedition. Go to Lowtown at night time and talk to Dougal Gavorn near the foundries. Agree to his offer to give you the 50 Sovereigns needed in exchange for double the return (100 Sovereigns). Then go to Bartrand in Hightown during the day to tell him the money will be delivered to him. This will initiate the Deep Roads Expedition quest.
The Deep Roads Expedition
After raising 50 Sovereigns (or alternatively, doing the Friends in Low Places quest) go to Bartrand in the Hightown Merchants Guild during the day. Make sure Varric is in your party when you talk to him. Also, once the expedition starts, Varric will be locked into your party. For the best cinematic events, we recommend you take your sibling and Anders along. Give Bartrand the coin and the maps. Before you set out on the expedition, make sure to finish all other quests you're interested in, including any companion, secondary, or side quests. Once you advance to act 2, you will not be able to go back and complete these quests. Make sure to make room in your inventory, as you will run into a lot of loot during this quest. Speak to Bartrand again once you are ready to embark on the expedition.
When you reach the collapsed path, offer to scout the side passages for a way around. One of the dwarves will also ask you to be on the lookout for his son that went missing, Sandal. Exit the camp and head towards the passageways. There will be lots of confrontations along the route, so be prepared. Find Sandal, and keep exploring. Defeat the Giant Ogre in one of the chambers ahead. Shortly after, be prepared to fight a dragon.
The expedition continues after that. You reach an abandoned thaig. Explore the thaig to see what secrets it holds. Find the door and enter the Primeval Thaig. Approach the Lyrium Idol. Bartrand will betray you at this stage and lock you in. Head south to look for another exit. Talk to the Demon and decide whether to accept his offer or not. For the most reward and XP, we recommend you reject his offer. Defeat the enemies and head east in the corridor. Defeat the Ancient Rock Wraith - prepare for a very hard battle. When it is floating on the air preparing its special attack, make sure all your party members take cover.
When you defeat it, loot all the chests to find the crypt key to unlock the crypt door, and leave for the surface. If Carver or Bethany is in your party, they will suffer from the Blight disease. If Anders is in your party he can help your sibling get into the Grey Wardens and save his or her life. Otherwise, you have to perform an act of mercy on them.
This concludes the Deep Roads Expedition quest as well as act one in Dragon Age II.