So... Back to the original topic, the intentions of the king are somewhat clear now.
[Theory + 166 Spoilers]: I think that Ashura "just" wanted to erase Fay's curses. Fay said in 166 that he doesn't get any stronger when using magic, he gets weaker until he dies. That means that he had the sealing tatoo made by the king probably to prevent this. Then Ashura started to kill people to get stronger, until his magics were stronger than Fay's and wanted to die by his hands triggering the first curse.
Fei Wong Reed said that if Fay were to kill the king he would die after (Perhaps because the overuse of magic), so I was thinking that the king made him the tatoo to save him from weakness until he died and give that Fay a chance to use his magic to flee from the second curse. [/Theory + 166 Spoilers]