Barkskin's actual name is Reaper, however most of those he works with know each other on a last name basis.
Reaper's basically a demon, notorious in his earlier day for causing quite a bit of chaos and destruction, it's his specialty after all. Mostly known for his work of reclaiming souls, taking down larger demons who've went against their plea bargains, and corrupting a few.
However, nowadays Reaper's losing his touch. His heart, after years of not beating has finally sparked back to life. Although this may sound sweet and a happily ever after, the more in love and selfless Reaper is, the more mortal he becomes.
You're the closest to heaven that I'll ever be.