You see Magus068, your theory is very good but, you see why would he want to lose his memories? But remember now FATE(remember FATE is alive in this time period) can see and control the future. FATE can see if he will tamper with time and if he dose, FATE can kill him. So perhaps he just wants to look after Schala/Kid, to understand how Schala is Kid, to see if Serge is worthy to marry into the Royal Zeal line, or maybe Belthasar used him as an agent to make sure things go as planed.