Nicodemus claimed that his goal was to save the world.... I think he was being completely truthful. It's just gone terribly wrong, and I agree you can't play with powers like Anduriel without being corrupted by them. Not forever. But, Nicodemus still thinks he's in charge, still thinks he's going to save the world.
Our little Nicky is probably the Nicodemus of the Bible (John 3:1-21; John 7:50-51 and John 19:39-42). Nicodemus comes to Jesus and they discuss whether one can be "born again" from above. Later, he questioned the appropriateness of Jesus' kangaroo trial before the Sanhedrin and then still later is said to have assisted Joseph of Arimathea in preparing Jesus for burial.
Our Nicky also has Judas' noose and the thirty coins, which also fits, given that Nicodemus was in the right place and time to grab those items. He also claims to be two thousand years old.
Btw, Nicodemus is a Saint in the Catholic Church, making that exchange with Harry all the more amusingly ironic when Harry remarks that Nicodemus will one day be a Saint.
But, Nicodemus' degradation is even more tragic. He was an actual Saint. Today, in his pride and arrogance, he's committed every conceivable crime and sin and has killed the only thing in the world that he appears to have loved. He can't admit to himself that he's not the one in charge.
Does anyone actually think that a Fallen Angel would ever consider a human an equal partner? If any Fallen Angel thought that, they would not have fallen. Some humans are more useful than others, more cooperative and effective when controlled more subtly.
Back to Marcone. Marcone may think he's a partner of Namshiel, and it may be that Namshiel's previous host was "weak" but Marcone will end up that way too, it just may take a long time. But, consider. Marcone is a gangster, he was thoroughly corrupt and degraded before taking up the coin. Unlike Nicodemus, Marcone was no Saint.
