Revanchion is a level 60 ghost... thing in Dire Maul: West. He's one of the more annoying-to-get-to invasion bosses. Not because he's all the way out in Feralas, but because he's in Dire Maul: West. To get to him you need the Crescent Key which is earned via a quest in Dire Maul: East. So he may be more trouble than he's worth, but that's not for me to decide!
If you're level 60 (or higher) I assume you know where Feralas is, I assume you know where Dire Maul is, so I'll forego the handy dandy map this time. If you have the Crescent Key, just run up into Dire Maul and get started. If you don't have the key, you can work around that by rounding up a bunch of ogres, letting them have their way with you by the door, releasing spirit, and rezzing on the other side. You bunch of cheaters.
When you're inside, there are some wandering trees you should deal with. If you're really good at timing and sticking together, you can get away with killing only one or two if you work around their patrols. On the other side, you'll come to a set of three archways.
The middle will lead you to Tendris Warpwood. We don't care about him. The right will lead to the upstairs section. We don't care about that either. Go left. You'll see an area like this:
See that ghost hanging out waayyy in the back in the corner? Like they should be wearing a dunce cap? That's Revanchion. Clear the trash here, then pull the boss!
The biggest problem when fighting this guy is he has an insanely high dodge rate and has Frost Armor. Your tanks will have very very low threat unless they're a Paladin, so be careful! Beyond that, the fight really isn't so scary. He has a Shadowbolt Volley he does now and then, but that's about it. He also melees, but it doesn't hurt much. Just kill him.
Unfortunately, the loot Revanchion drops isn't as good as the drops you were getting from earlier invasion bosses. At level 60, Outland gear is available to you, and that stuff is amazing. Back in 2006, though? Before epics were commonplace, and before we even had access to Outland? This stuff was top of the line.
So what does he have? He has some healing bracers, Bracers of Mending. Though with the spell power change, some regular caster could get use out of those! Shadow Priests would enjoy that Spirit for leveling, for example. There are some spell power gloves, The Shadow's Grasp. Melee classes can bask in the not-quite-glory of the Cloak of Revanchion. Lastly, he drops Corruptor's Scourgestones if you're wearing your Argent Dawn Commission (or similar trinkets) just in case you're working on Argent Dawn rep for achievements.
If you've never done Dire Maul before now, I recommend taking this opportunity to run through it. Heck, do all three wings if you can. They all tie together a bit while still having their own individual stories. It's a bit like what Burning Crusade dungeons should have been. It has wings, but they're all interconnected in little ways. You can go from one to the next without every stepping out of the instance if you want to do so. It's neat! Explore!
Now, let's go back to the Eastern Kingdoms with Lord Blackwood!