I'd be surprised if WotC let Obsidian rewrite their cosmology. Since nobody else is bothering with spoiler tags, I won't either to say this, despite my best efforts, I wasn't able to bring Myrkul back. I wanted to be his friiiend. But no, he wanted to be a jerk, so I had to beat him up. Same thing. Obsidian probably isn't allowed to resurrect Myrkul anymore than they are allowed to tear down the wall. Or any more than you could have resurrected Bhaal in Baldur's Gate. I would have loved to have tried.