This mod has been conceptualized back in October as dedicated thing for 10th anniversary of Pixel Dungeon becoming free and open source software, but only now I dedicated the time to start making it. The core idea is that I am not the one, who design the features and new items, it's people from community of this game!
I think the rat king curse is a bit strange, since it not only dooms the run to fail and has no counter, using a scroll of rage, terror, or retribution can trigger it if it spawns near the boss room, which it often does. Maybe have the rat king turn hostile and have better stats than sewer rats?
A bit Tolkein, but a ring that allows up to 9 other rings be worn, however, the more rings one has, the more curses the one ring applies. Also, if a Remove Curse is used on the one ring, it will destroy a random ring.
Also, could we get a listing of the 20 features so that we don't request something already added?