Man, im so lazy. I disassembled him three weeks ago(!) and im posting him now..
But lets get to the moc. The main idea is, that his body becomes penetrable (immaterial or something like that) but the chain on his back does not. This means his fight style is based on baiting enemy to rush at him and stop at chain. Obviously he can't be immaterial for long time, it's around 30 seconds and a minute to recover, this means he need to time it well or he will get in trouble.