He's at the top of the tower, the hardest to get to as you have to clear several bosses to do it and TBH if you're new you should do Aran to else it's a LOOOOOONG run.
You can, as a bare minimum go Entrance -> Moroes -> Opera -> Curator -> Chess -> Prince but there is a lot of stuff in the way (like 45 mins of trash I reckon between Curator and Chess) and if you did there is a lot to clear.
The normal route we take is Attuman -> Moroes (to stop the trash repopping in the ballroom) -> Maiden -> Opera (mandatory to get to the upper level) -> Curator (cannot skip him) -> Aran (allows you to portal to the library so saves run time) -> Chess -> Prince -> Netherspite -> Illhoof -> Nightbane (sometimes Nightbane before Curator).
You can, as a bare minimum go Entrance -> Moroes -> Opera -> Curator -> Chess -> Prince but there is a lot of stuff in the way (like 45 mins of trash I reckon between Curator and Chess) and if you did there is a lot to clear.
The normal route we take is Attuman -> Moroes (to stop the trash repopping in the ballroom) -> Maiden -> Opera (mandatory to get to the upper level) -> Curator (cannot skip him) -> Aran (allows you to portal to the library so saves run time) -> Chess -> Prince -> Netherspite -> Illhoof -> Nightbane (sometimes Nightbane before Curator).