Before getting your hopes up though, it seems very unlikely that this quest will lead to earning the actual item again. Blizzard has repeatedly commented on the exclusivity of rewards, going so far as to state outright that the Corrupted Ashbringer would not be reintroduced as an earnable cosmetic/transmog reward.
Group Interview with Ion Hazzikostas
They want to add ways to get appearances that exist in the game that are no longer available / have never been available back into players’ hands. They want to hopefully get to a point where there are no remaining things in that backlog, other than ones that are very deliberately no longer available like Corrupted Ashbringer.
That said, this quest clearly leads to something. It could be a part of the Patch 10.1.5 campaign and upcoming Dawn of the Infinite mega-dungeon, or it could be associated with the new rewards from Naxxramas – which seems to be receiving a similar treatment to Zul’Gurub in Patch 10.0.7. Only time, through the machinations of the Infinite Dragonflight, will tell.
New Naxxramas Rewards in 10.1.5
New Mount
The biggest addition is Valiance, a new mount that has the source as itself, meaning it will likely spawn inside the old raid. This mount has the model of the mount used by Thane Korth’azz in Naxxramas.
