Once you defeat Ultraxion you've got to chase off after Deathwing. Thrall may have hit him with the Dragon Soul, but it was only enough to break one of the armor plates on his back. It wasn't enough to do serious damage to him. And if he makes it back to the Maelstrom and through to Deepholm he'll get that repaired quite easily.
Sky Captain Swayze says: Welcome aboard the Skyfire. You ready to chase down the end of the world?
<Player> responds: We are the Horde. We are always ready.
(Booyah! Horde! /roar)
So off you go on the Alliance gunship. Deathwing, bastard that he is, destroyed the Horde gunship so everyone piles on to the Alliance gunship to follow Deathwing before he reaches the Maelstrom.
The sixth boss in Dragon Soul is Warmaster Blackhorn. He's a Tauren Warrior who flys in on his trusty twilight drake, Goriona. He is accompanied by a variety of twilight drakes, Vrykul dragonriders, and a few goblin sappers. He is here to delay and destroy the gunship so that the Aspects can't use the Dragon Soul again before Deathwing makes it to the Maelstrom.
Sky Captain Swayze says: We're catching up to the dragon! I think I can make him out through the cloud cover!
<Player> responds: Bring us in closer!
And that starts the boss fight! Blackhorn swoops in and destroys the Skyfire's engines.
Sky Captain Swayze yells: All ahead full. Everything depends on our speed! We can't let the Destroyer get away!
Warmaster Blackhorn yells: Hah! I was hoping you'd make it this far. You'd best be ready for a real fight.
Blackhorn rides Goriona around to set all four engines on fire.
Sky Captain Swayze yells: Our engines are damaged! We're sitting ducks up here!
Warmaster Blackhorn yells: You won't get near the Master. Dragonriders, attack!
Sky Captain Swayze yells: All hands to battle stations; get those monsters away from the ship!
Swayze's voice and accent kind of drives me insane. It's excellent voice acting, he definitely has both confidence and a sort of unbridled panic that I'd imagine I'd also have if a dragon had set fire to my airship. I call him a Westfall Redneck whenever I can.
For the first phase of the fight Blackhorn sits on his drake and bombards the boat with a big Twilight Onslaught every now and then. Everyone needs to stand in that big purple swirly to make sure the damage is spread out between the group. The tank holding the cleaving melee add, if it's not dead, should make sure that the cleaves are pointed away from the rest of the raid.
Meanwhile ranged will burn the crap out of the drakes, and melee will take care of the Vrykul who drop to the deck. Everyone has to swap and stun/slow/kill sappers as they show up. The smaller drakes are dropping little purple swirlies constantly. Everyone has to stand in as many of those little purple swirlies as they can. For normal that means making sure that you're at full health. For heroic that means having a buddy, and not standing in one more than every fifteen seconds or the nasty debuff they put on you will slaughter you.
Warmaster Blackhorn yells: Goriona! Give them hell!
Second phase starts when the last of the six twilight drakes dies. At that point the melee mop up any remaining Vrykul adds and kill the last sapper that appears. The ranged will do their best to hurt Goriona until she flies off (or lands in heroic). Everyone will be dodging the fire that Goriona drops and the cone of damage that Blackhorn does. Meanwhile one tank will pick up Blackhorn himself and keep him close to the center of the boat. The tanks will swap off every two stacks of the nasty armor reducing debuff.
Heroic mode has Goriona land on the deck and need to be tanked. This slightly complicates the tanking as the two tanks will need to be speedy with the taunt. Also in heroic there is a nasty debuff. This needs to be healed off, but will aoe the raid for the amount of healing it absorbs. So it needs to be gradually healed off.
Apparently I have never actually managed to get a shot of Blackhorn dropping to the deck. Even now I'm too busy trying to taunt him before he eats a healer. But if I'd managed to get a shot, as he hopped off his dragon, he'd say:
Warmaster Blackhorn yells: Looks like I'm doing this myself. Good!
Warmaster Blackhorn yells: Well... done, heh. But I wonder if you're good enough... to best him.