General Hospital and Supernatural alum, Sebastian Roché will be un-tombed very shorty and thanks to Zap2it I have some spoilery bits to share about his character Mikael; and yes, that's the correct spelling. The Vampire Diaries is serious about protecting the authenticity and old-world origins of their characters ;).
It remains to be seen for sure whether Mikael is an Original vampire. There's a notable absence of a white-oak silver dagger in his chest when Katherine opens the tomb. However, he is wrapped in chains, and has clearly dessicated without being able to feed on blood, so it's likely that he was never killed by a dagger or a stake -- just stuck in the tomb, as the 1864 vampires were in Season 1.
The general consensus is that Mikael may be the Original father -- that is, Rebekah and Elijah's father. We know that the Original dad had quite a temper, since he killed the werewolf who fathered Klaus. But is his temper dangerous enough that he would hunt his own children? Remember, Klaus wasn't the only one on the run from Mikael in the 1920s. Rebekah feared him as well.
We know that Mikael was entombed by a witch in the Pickett wing of the largest cemetery in Charlotte at some point in the 1990s. Given that this is "The Vampire Diaries," we have to assume that there's some significance to that time frame... and our first thought is that Elena, the first viable doppelganger in five centuries, was born right around then. And how convenient that at the time of his capture, Mikael was in the Southeast United States, the birthplace of the doppelganger.