@MarshalTobias32 Honestly speaking he's not that much of a challenge. Say, the first ~100 floors while you're still learning and Masquerade is going through rapid changes can be challenging. However after that it quickly becomes an annoying daily chore. The next significant bump in challenge comes at 990-998, and of course 999 which is a challenge of its own because he will literally one shot you no matter what. Only death resist effects can save you from his hits. (Do keep in mind that you have 998 depths worth of no hit practice runs).
The main problem here is, once you reach depth ~100(?) the rate at which he goes through changes slows down to a crawl. It takes literally hundreds of depths for you to see any significant changes and by the time you reach those you already know the fight inside out. The new mechanic changes might get you a few times, but after that the fight returns back to being an annoying chore for the next few hundred depths.