Not to be confused with Frostbite, a weapon by another user
The Frostbite is a Post-Moon Lord worm boss.
The Frostbite spawns in the snow biome at in the same way the King Slime does, so water candles can help.
The Frostbite attacks the same way as the Eater of Worlds but it also spawns Ice Slimes.
Ethanius - Pixelfalls
Note that this is not what the song would be, but it would be similar.