This thing's a behemoth. You probably saw him as you were dashing through the ramparts (if you looked down at least). Ultimately, Raigonn manages to break through the first gate. Left unchecked, he could break open another gate. Raigonn has an unbelieveably tough exterior which reduces damage taken to almost nothing. Your party needs to somehow remove that vulnerability before you can tackle Raigonn head on.
World of Warcraft