Doomrider is apparently in the Master of the Hunt book from the Black Library, which is apparently a book about the White Scars on a Great Hunt with Khan. Doomrider is the most excellent adversary, and there was some shock and dismay yesterday with the conclusion of the book.
So Please do not read further if you do not want the end spoiled.
While I have not read the book, it was apparently noted on both Warseer and the Bols lounge that the Doomrider dies in this book, while severed from the Warp. So is he gone from our game for good? I know a lot of people were hoping he would come back in a dataslate. At least I was.
Please note, that I have not read the book.
The idea of an army backed by lots of chaos bikers led by the Doomrider is a great image. Even though he apparently dies, who knows if we will see some incarnation of him appear in the future. The backstory would definitely be very interesting now with his sudden demise.
Who is the Dooomrider?
via 40k wiki
Doomrider is a Daemon Prince and one of the strangest servants of the Chaos God Slaanesh. His true identity has been lost to time and all that is known of his past is that he was once a Space Marine Biker of the Emperor's Children Legion. Having been granted Daemonhood by Slaanesh, Doomrider now eternally rides through both the Materium and Immaterium, always in search of new sensations. His love of speed would put an Ork Speed Freek to shame, and it is only equalled by his love of bringing agonising death to the denizens of the Materium. Servants of Slaanesh often attempt to summon him forth from the Warp to assist them in battle, but even when they succeed in attracting the Daemon Prince's attention, the vain and fickle Doomrider usually disappears back into the Warp soon after his arrival regardless of the outcome of the combat in search of the next happenstance that has caught his attention.
The Ordo Malleus has identified and translated the following blasphemous refrain into Low Gothic as the core chant of any sorcerous ritual attempting to summon Doomrider:
Oh great Lord Slaanesh, send forth your servant, the Daemon Prince Doomrider! Let our enemies tremble in raptured awe before his fearsome visage!
Grant them an exquisite death, crushed beneath the flaming wheels of his chromium steed! Permit them the ecstasy of being slaughtered by Doomrider's throbbing Daemonsword and his pulsating gun of gushing plasma!
Bestow on them one fleeting moment of pleasure as they stare in wonder and orgasmic delight at one of your most divine creations before dying at his hand!
Oh great Lord Slaanesh, for these reasons and many others that tease and titillate our imaginations, we beseech you, send forth your servant, the Daemon Prince Doomrider!