The Energon Pub

[Gyro-Robo]

Let's get ready to rumble!

[Shadowman]

I haven't seen the season finale of Adventure Time, but Arthas was only killed when Tirion managed to pull a Deus Ex Machina and shatter Frostmourne with a weapon specifically designed to be devastating to the undead, and finished him off as all of the souls contained within held him down, after Arthas wiped out the army that came to kill him, in a single hit. And even then, that didn't stop him. It killed Arthas, but Ner'zhul is still only MIA, and the title and abilities of the Lich King were passed on.

[Twitchythe3rd]

Pretty much.

The Lich King himself is just a spirit bound to the helm. His mortal host can die, but he lives on. Whoever wears the helm becomes the new Lich King.

Arthas was only the first. Tirion was going to take it next, but Bolvar interjected and took on the burden instead.

[snavej]

So he's fighting himself? He's not that stupid. 'New voices' Rick and Morty win.