@Ree  
In “Mortal Recoil” The Lich was able to possess princess bubblegum  
 
As well as this snail.  
 
Prismo said that the Lich Billy was a “Ghost wearing a dead guy.” in “Finn”.  
 
And the Lich’s origins seem to lie in the mushroom bomb that made Ooo how it is, since he first appeared from the crater, then in “Jake” Jake was transformed into him.  
 
 
This leads to the conclusion that unlike a normal lich, the lich is a ghost that possesses bodies every time it needs a new one, instead of growing one from its phylactery.

@Greenjack  
Actually you’d be dead too.

@Ree  
i believe its an everyones show

I wish that the lich wished for eight seasons.

the fuck just happened? did he just kill my ponies?! THERE ARE NO CURSES THAT ADEQUATELY DESCRIBE THE HORROR YOU HAVE CURSED THINE SELF WITH THIS DAY YOU FILTHY CUR! YOU KNOW NOT THE WRATH I BEAR, YET YOU SHALL KNOW IT SOON!!!

LordAnubis> Actually, he didn’t so much “impersonate him” as he tore the skin off his body and wore it as a disguise.
 
Kids show…..

@Rarity Fan
 
It also implied be killed Billy’s old lady girlfriend and probably the bear if it wasn’t useful anymore.

@LordAnubis
 
The Lich killed and impersonated him, it was in the last season’s finale.

Holy shit, is that Billy? The fuck happened to him?

das wut