Ok, this mod is REALLY BIG! Really, REALLY BIG!!!
All the things you need in wiki page
Shortly about mod:
All the alchemistry are useable for fighting
That's all that you need if you don't want spoilers
Now I'll tell you about things that you must know if you want to complete this mod
First of all, read the wiki. Completion of mod is slaying Devil. You can summon him by Imp Heart. Imps - hell creatures. You can see them only if you have used Contract with Devil.
Other mobs just will spawn in your world