This item is acquired in-game. See its sources below.
Not sold on the Auction House·Weapon
An Epic Dagger One-Hand, item level 441, requires level 70, binds when picked up. Drops from Tindral Sageswift, Seer of the Flame in Amirdrassil, the Dream's Hope.
First seen in build 12.0.7.68887 (Midnight (patch 12.0.7)).
Related
Betrayer's Cinderblade Game Data
Appearance
In the Appearances collection, Betrayer's Cinderblade is listed as Boss Drop. Appearance IDs: 82183, 82185, 82186, 82188. 4 other items wear the same appearance:
Blizzard numbers items as they are created, so the named items next to ID 207781 (207776 to 207786) were usually added in the same batch as Betrayer's Cinderblade: the same quest line, zone, vendor or reward set.