It kind of makes sense because he seems very old, but how old really? He guards a place where the dead can come to the Far Shores directly, which needs a true and devout keeper that has no chance of turning on the souls. Tu'whacca could be this keeper, because he truly cares about the dead reaching a good place in death. Another thing that strikes me as suspicious is when you get to the area with Septima Tharn, the keeper appears in the sky saying that if you kill her, you can take the kings soul back to the land of the living where he can live the rest of his life. I would think only Tu'whacca would say this, for he is the god of burials. One last idea is that the keeper is in disguise as the God of Nobody Really Cares who shouldn't be too much of a suspicious disguise because nobody should really care other than people past the 4th wall (us).