The Witcher 3: 10 Hardest Boss Battles You MUST Find
4. The Phantom Of Eldberg
The Phantom of Eldberg is another spooky battle that can be found in Eldberg Lighthouse, in Skellige.
The Phantom itself is a very powerful Penitent residing at the top of the lighthouse, which is also chock full of wraiths and other horrors for you to viciously twirl through (or scream and run away from).
While the Penitent is strong on its own, being completely invulnerable except for a short time when Yrden is used, it also can't be killed until a few other objectives have been completed, turning the fight into a deadly war of attrition. You can drink enough potions to sink your shiny new rowboat, but unless you solve the mystery of the lighthouse, you ain't killing anything.
What's particularly interesting about this fight is how many quests tie into this one. You can find out about the lighthouse in a number of different ways on Skellige, like fighting Madman Lugos for example, and there's more endings to this quest than there usually is, depending on what other quests you've completed.
You can even end up thrown in jail, if you've not followed a few specific steps beforehand. Still, at least you got to be Geralt, the fifth Ghostbuster for short while.