Who is the person you slay at the end of your first playthrough?

Major Dead Cells spoilers, for those who haven't experienced the game yet.

You find out your true identity as

The King after defeating the Giant for the first time.

But if that's true, who's the guy at the end of your first playthrough?

Spoiler alert!

Note that the King you kill in the first playthrough is a lifeless husk; this is because the soul of the King, the player, is no longer in the body. This was caused by the experiments between the King and Alchemist going wrong.

If you haven't finished the game yet, this next bit will be even more of a spoiler.

Eventually, the Time Keeper reset the timeline properly, and after defeating the Hand of the King, you merge with the King, but are infected with Malaise. So, you go to fight the Collector in order to get Panacea to cure yourself. The game concludes with the King (player) stating he had more fun crawling around in the sewers.