What is Ghostcrawler?

Ghostcrawler is a who not a what. ;) As for his job description and what he and his team do, you can read it in his own words from a much older thread here- http://forums.worldofwarcraft.com/thread.html?topicId=14134474969&sid=1&pageNo=6#111

Q u o t e:
We generally use "developer" to mean someone who works on the game itself, as opposed to people in other departments of Blizzard who support production of the game. Blizzard is a place where feedback is very important though, so people throughout the company still tend to have a pretty big impact on game design.

I am a game designer, and specifically I am the lead systems designer for WoW. Game designers are not artists or programmers, but we use the tools developed by the programmers and the assets created by the artists to get content into the game. Programmers make the game run, artists make it beautiful, but it is the designer's job to make it fun. (Though again, Blizzard collaborates more than many studios do and I spend a lot of time talking to programmers or artists about class, mechanics or even achievement design.) I think a lot of players mistake me for a CM because I tend to post a lot more than most WoW designers. Mostly, I just don't sleep so it lets me play WoW, work on it during the day and still have time to post. :) Game balance is one of the most controversial aspects of any multiplayer game, and I benefit from being able to engage the community directly. Systems design specifically is everything that is not level, story, quest or encounter design. My team handles everything from classes to mechanics to items to trade skills to achievements to UI design, and that includes the game balance.

I do want to stress that we are a team. We come to a consensus on every major change to the game. I put enormous faith in the team to make the right call and keep any of us individually from doing something stupid. Blizzard is in a position to be able to attract and retain the best talent available in this industry. Many of them are much better game designers than I will ever be. Mostly I try and stay out of their way. A great many of them read the forums. Everything you type is seen by silent blues. I see people reading the forums when I drop by their office. We talk about what they have read all the time. These guys care passionately about doing the right thing and making the game as good as they can. Your opinion is extremely important to them. Just keep that in mind every time you post. :)