I have some feedback after playing the mod for some time.
1. Rebellious Wisps are far too rare. I barely ever find any. They also should not spawn if you're in front of a wall, like Wyverns, because they can destroy an early pre-hardmode character even inside a house.
2. The Oneshot is pretty difficult considering when it's supposed to be fought. Perhaps a bit too difficult, to be honest.
3. The firecaster scepter doesn't seem to use mana correctly. It uses it once then you can hold it down forever. Its droprate from Shadow Casters is also far too low. I didn't get one until I was over 30 nights into the game.
4. Switch Casters are too rare in the dungeon, given how rare the Bone Ring is to drop from them.
5. The Full Colour is kind of useless compared to other weapons. It uses too much mana, fires at an average speed, and does good but not great damage with no piercing or anything.
6. Sentinels are annoying, since they often attack from offscreen and hide inside blocks where you can't hit them.
7. The "quest" system is really cool! One suggestion I have, though, is to be able to get the Reading Glasses back, or make a copy of them, rather, after returning them to the Librarian. They're great vanity and have a decent effect but I feel wrong not giving them back.
8. I don't know why, but after Skeletron, the Frozen Ship no longer has its unique music, and the spawnrate of Witnesses went down a lot.
9. The Moon Prince helmet hides beards when it shouldn't. Same with the Spirit Hood.
10. Also, I understand English is a very hard language. As a native speaker, I say it's awful and a linguistic abomination. However, especially given the (comparatively) story-focused nature of the mod, I feel you should make it a priority to get someone on the team to be a translator. While the current English is passable, it is awkward in many places, and sometimes hard to understand.