She won't be a playable character though
BioWare has confirmed that fan-favorite character Morrigan will return in Dragon Age: Inquisition. Speaking to Game Informer, writer David Gaider says "It's not a cameo. She plays a significant role," but it was also revealed that Morrigan wouldn't be a playable party member.
Morrigan was one of the standout characters from the first Dragon Age game but she was absent from Dragon Age II. Absence surely makes the heart fonder and the powerful witch will be the central in the new game. "The story of Inquisition is [Morrigan's] moment," says creative directore Mark Laidlaw. "[She] has a human role in this plot," adds Gaider, "which I think may surprise some people because they might only think of her as a plot device."
The ending of Origins and the Witch Hunt DLC showed Morrigan had her own agenda and plans and her reappearance in will surely signal some upheaval. Whilst I'm glad BioWare is expanding on some of the main plot points from Origins, I'd be really be happy to see some more info on the mechanics. That was the main turnoff for me coming from Dragon Age: Origins to its sequel.
Dragon Age: Inquisition’s Morrigan – Past and Present [Game Informer]
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