Morrigan wishes to talk. She has a plan to counter Corypheus and his dragon.
Obtained upon completion of What Pride Had Wrought.
Head to the room with the eluvian near the Skyhold garden where you will meet Leliana. She tells you that Morrigan has entered the eluvian in pursuit of her son, Kieran. You are informed that Kieran activated the eluvian and went through himself causing Morrigan to follow. Enter the eluvian after Leliana races off to get help.
To the Inquisitor's surprise, the eluvian leads to The Fade and not the Crossroads. Head south and speak with Morrigan and she will ask you to help her look for Kieran just a little longer. Continue south, west then north and you will find Kieran with Flemeth. Kieran informs his mother that he heard Flemeth calling to him through the mirror and that "it was time." The cutscene continues, revealing some startling information.
If Morrigan drank from the Well of Sorrows, she attacks Flemeth in order to protect Kieran but Flemeth simply dispels her magic. It becomes apparent that Flemeth is in fact a vessel for the elven goddess Mythal, giving her control over Morrigan's actions.
If the Inquisitor drank from the well, he/she will be the one to stop Morrigan when she attacks.
Flemeth then offers a deal. Morrigan can give up Kieran, with the promise that she will be free of Flemeth from that point on. Or, Flemeth will return Kieran to Morrigan but will never stop pursuing her. Morrigan chooses her son and instead offers her own body to Flemeth in order to spare him. Moved by Morrigan's love for her son, Flemeth takes the Old God soul from Kieran but otherwise leaves him be. Before she departs, Flemeth tells Morrigan that she could never possess an unwilling host and that Morrigan was never in any danger from her.
The Inquisitor, Morrigan and Kieran return to Skyhold through the eluvian to ponder the implications of everything they've discovered. If Morrigan was the one to drink from the well, she informs the Inquisitor that she can match Corypheus's red lyrium dragon in battle and that it is up to the Inquisitor to find Corypheus and his pet.
If Morrigan's Ritual was not completed during Dragon Age: Origins:
If Morrigan drinks from the Well of Sorrows, she informs the Inquisitor that she has found a way to match the red lyrium dragon's power. She informs the Inquisitor that they must summon Mythal and requests that the Inquisitor be present at the Altar of Mythal located in the Arbor Wilds for the summoning ritual in case plans go awry or guardians are encountered.
Upon travelling to the Altar of Mythal and using it. Morrigan summons Mythal. Much to her surprise, Flemeth appears and explains that Mythal is a part of her. Mythal was the spirit which helped Flemeth seek vengeance on her husband in the past. Morrigan is therefore bound to the will of Flemeth. Flemeth then passes on knowledge to Morrigan, allowing her to match the red lyrium dragon in power.
If the Inquisitor drinks from the Well, the voices of Mythal's servants will instruct them to go to the Altar of Mythal and perform the summoning ritual at the Altar, to which Morrigan shows up, despite not being asked to. Following the summoning, Flemeth appears and when Morrigan tries to attack her, she is stopped by the Inquisitor.
Flemeth informs them that the Guardian of Mythal will appear, and if they manage to defeat and master it, it can be used against Corypheus. The guardian is a fire damage dragon of the same level as the inquisitor. It is immune to fire damage and vulnerable to cold, and has no guard or barrier. When it is at half health, it is tamed and the combat is over. The dragon flies away, and this completes the quest and the Inquisitor returns to Skyhold.
A chest containing a Superb Belt of Spirit Resistance and other random items.
Completing this quest triggers the game's final main quest, Doom Upon All the World.