Are you referring to rumored [Alternate ending](http://deathnotefanon.wikia.com/wiki/Alternative_ending) of Death note?

From [deathnotefanon.wikia.com][1] :

> The Death Note alternative ending is a possible ending to show
> something else that might have happened to Light Yagami after his
> death. It is unknown if the ending is real or fake. There is a lack of
> evidence to prove the ending to be real. It has really only been seen
> on the Internet and there are mainly English versions of the ending
> circulating, but it has become popular in the Death Note fandom.
> 
> Due to the fact that there is no proof, it’s left to fans to decide
> for themselves. **The ending only exists in manga form**; there is no
> anime adaptation for the ending.


But in this ending Light decide to die in old age and tell Ryuk to kill him. After his death he appear in Shinigami Realm and started dying gain again in the way his victim died. Then light tell Ryuk to take him to there king, so that he can make deal with him. He even told that he will kill there kind if he didn't agreed. But in the end they just showed start of there journey, no interaction  with king.

 
  [1]: http://deathnotefanon.wikia.com/wiki/Alternative_ending