Neverwinter
210 Achievements
3,045
1000+h
Dancing on the Ceiling
You defeated Cthylar 5 times while fighting on the ceiling
10
0.6%
How to unlock the Dancing on the Ceiling achievement in Neverwinter - Definitive Guide
The required item level for Castle Never is 2000, but you definitely want to be at least 2,500+. To make things much easier, I would suggest having a bubble paladin with high recovery or a paladin and haste cleric combination.
Here is a video showing my group successfully killing Cthylar on the ceiling. Note that after killing him, the battlefield automatically inverts to normal, so it may not immediately be clear if you succeeded or if he flipped at the last second.
To check your progress on this achievement, go to Journal > Achievements >Dungeons.
During the cutscene that introduces Cthylar, it will actually make a visual reference to the spikes on the ceiling. Cthylar will invert to the ceiling and revert to the floor approximately every 35 seconds. Once this happens you want to defeat him on the ceiling. Otherwise the fight is fairly straightforward; he will spawn small amounts of adds from time to time.
With enough DPS you should be able to whittle him down below half health. Once the inversion happens, lean into him with your best rotations, artifacts and dailies to defeat him on the spiked ceiling. If your DPS output isn't great, just keep at him and wait until the next cycle when he inverts to the ceiling again to get him. Upon his death you revert back to the floor immediately; which is slightly annoying because it makes it seem like you didn't kill him on the ceiling...but it should count.