After getting the three-blade harpoon, Han Sen had no time to play with it before he was brought to Son of Heaven by Huangfu Pingqing.
Son of Heaven obviously already knew that he would come. The conditions offered to Han Sen were part of the agreement between him and Huangfu.
If it was not for the fact that the Mystery Island would only last for a short time, Son of Heaven would never have agreed to ask for help from Han Sen, let alone offer him benefits.
What he did not know was that it was useless to promise Han Sen anything, because the Holy Angel was already killed by Han Sen.
