A New Path is a companion quest for Merrill in Act III of Dragon Age II. You will receive it after accepting "Best Served Cold" quest (available regardless of whether or not you gave her the Dalish tool arulin'holm in the quest Mirror Image).
Quest
- If you gave Merrill the arulin'holm during the Mirror Image quest in Act II, she starts this quest by saying the tool wasn't enough to fix the Eluvian, then asks that you help her go to a demon for more information and its help.
- If you refused to give Merrill the Dalish tool, she will start this quest by saying she needs to speak with a demon for another way to fix the mirror. She asks you to go along in case things go wrong and, even if friendship is in rivalry, will say she trusts you.
- Accepting the quest without question nets
Merrill: friendship (+10) - If you accept the quest you can also say that she should talk to Marethari first (
Merrill: rivalry (+10)) or you can force Merrill to without asking by just talking to Marethari before hand. If you pick this route, and ask Marethari to "talk some sense into Merrill" you'll earn Merrill: rivalry (+10), or 
Merrill: friendship (+10) for asking Marethari to help fix the eluvian. Marethari warns Merrill not to seek the demon's help but no matter what she won't listen. - After climbing Sundermount you go into the demon's cave and find that Marethari has allowed the demon to posses her so that Merrill can't fix the Eluvian (This happens whether you talk to Marethari or not). She goes on to say the demon would have gone through the Eluvian once complete to ravage the world with Merrill as its first victim. You are then forced to kill the pride abomination (see Pride Demon) Marethari (it even pretends to die and become Marethari again before being defeated).
- After killing the demon Merrill is very distressed and just wants to leave. Upon exiting the cave you are confronted by the other Dalish who say Marethari came up here and hasn't returned.
Outcome
- If Hawke says that Marethari was possessed or orders the Dalish hunters to stand down, the hunters will attack, and later, when the party returns to the Dalish campsite, they will be attacked by every Dalish in the area. You will get Merill: friendship (+10) Fenris: rivalry (+10). Also rather than bemoaning her foolishness (If Hawke takes responsibility), she will be distraught that everyone was killed when speaking to her after the events that transpired and breaks the mirror regardless of your friendship/rivalry with her.
- If Hawke says that Merrill's blood magic was responsible for Marethari's death, and promises to take her away from Sundermount, the party will be allowed to leave. At the campsite, all of the Dalish behave as if the quest had not taken place. You get Merill: rivalry (+15) and Fenris: friendship (+10) if you take this path.
Rewards
After finishing the Quest you will have Keeper Marethari's Staff "Torch of Falon'Din" in your Inventory.
Bugs
- The quest can completely break before it begins. Merrill will begin the closing dialog of the quest before the opening dialog, so even though the quest is started in the story, the game considers the quest closed. Talking to Alistair later somehow starts the quest again (although the conversation is unrelated, this is likely a glitch), avoiding the previous dialog problem. The console can be used on the PC to fix this issue. Alternatively, sometimes talking to Merrill directly after the closing dialogue will trigger the quest as normal, without having to reload.
- At the end of this quest you can get stuck with Merrill in your party whether you choose to get attacked by the Dalish or to have them just walk away, to remove her from your party, simple return to your estate which should remove everyone and then just add who you wish to continue with.
- After Marethari's death, if Isabela left the party permanently in the quest To Catch a Thief, Isabela gains +10 friendship if you choose the option "Stand Down" to the Dalish.
- PS3, Merril breaks the mirror saying that she can never go back to the tribe...aaaand im not sure if I can continue the quest yet...needed of course for my supplier and platinum trophies...edit this out soon hopefully with an answer.