Speak with Mor'zul Bloodbringer at the Altar of Storms in the Burning Steppes.
<name>, your delvings into the dark arts are deep. Your mastery over otherworldly denizens has grown so strong... perhaps you are ready to bind to you one of the infamous dreadsteeds.
The ritual to summon the beast from its home requires great power and resources, but if you desire to dominate that epic mount, then speak with Mor'zul Bloodbringer. He is camped near the Altar of Storms in the Burning Steppes.
Go, <name>. This quest will be perilous, but a Warlock of your stature does not shy from danger!
Greetings, <name>, and welcome. Are you here to study near the Altar of Storms as I am, perhaps to harness its energy for some hidden purpose...
Or... are you here to speak with me? Yes, I believe you are.
You want to master a dreadsteed? Such is no easy task. It will cost you no small amounts of blood, sweat... and of course gold. But a dreadsteed of Xoroth is a prize well worth winning so if interested, listen on...