Where did that come up
Yogg was the reason the old gods were able to invade the emerald dream. N'zoth is the current primary source of corruption.
<SPK> US 8th Xavius Mythic - US 10th Helya Mythic - US 8th Gul'dan Mythic - US 9th Kil'jaeden Mythic - US 12th Argus Mythic
7/7M Emerald Nightmare - 3/3M Trial of Valor - 10/10M Nighthold - 9/9M Tomb of Sargeras - 11/11M Antorus the Burning Throne
World first heroic Gul'dan. Almost Wildstar hardcore status.
"I am the lucid dream, the monster in your nightmares, the Fiend of a Thousand Faces"
It has been described in Chronicles as well. Basically, fandral is crazy about planting trees everywhere so they planted one in Northrend (you can see whats left of it in Grizzly hills) and the roots went so deep that they got under the influence of Yogg and he took it from there.
"confirmed" ? no
Be feared, or be fuel
This was actually already confirmed through the Chronicles book, and later tweets. Yogg-Saron basically came up with the Nightmare, and got the Old Gods acces into the Dream.
Of course he is no longer holding the reigns of it. We should be seeking N'Zoth for that. Even if Xavius is seemingly standing with the Burning Legion, the power he uses clearly belongs to the Old Gods. And I doubt N'Zoth would allow that if it didn't serve his own goals perfectly.
1. Post this on lore forum.
2. Put Spoiler tag next time you want to unleash "new" informations about the lore.
3. Its not new.
Yogg-Saron proximity to the Grizzly Maw World Tree (dont remember the name) gave the Old Gods access to the Emerald Dream. After Yogg was imprisoned, N'zoth took over as the main source of corruption... until Xavius betrayed the Old Gods and became an ally of the Legion. Now the Nightmare is spread by the Legion.
Chronicles Volume 1 already confirmed this.