It did seem rushed. Sloane's character has been all over the board through the series, you never really knew where he was coming from, same with Iyena.
And anyone else remember an old DC "Tales of Krypton" where a scientist discovered the secret of immortality was a Kryptonian beast, but by using a serum on himself he turned himself into a humanoid version of the beast, thus ostracizing himself from humanity and ultimately being the completely alone and trapped by his immortality?
There's also the Star Trek where the matter and anti-matter guy are trapped forever in eternal struggle against each other between dimensions. I kind of envisioned something like that for Sloane and Jack.