A mere in Universe message; just to trigger OP. 
Dear strongest of Male Blood elf Death Knights, why are you serving the Horde as mere slaves? We recognize your potential, Join the Ren’dorei and you’ll be given food, comfort, as well as the most powerful sets of Armor, you no longer have to compete with Orcish Warriors or Tauren Sunwalkers, your physical Might and terrifying appearance will be praised and worshipped in the Alliance.
In exchange, you provide us with protection and breed with our women to produce powerful offspring; for the purpose of growing the Ren’dorei’s militaristic Forces.
Instead of the Lifestyle of mere feral savages scatter around the world; frantically attacking hostile factions trying to kill you, you’ll be granted the opportunity to live as Nobles and be provided with a purpose.