Quest Machine is a full-featured, extensible quest system that lets you add procedurally-generated and hand-written quests to your project.
I bought the asset today and I am totally blown away….it is extremely artist friendly with great, easy to follow documentation. I was able to make my first, quite complex quests in no time. It does everything I will need to make quests, even procedural ones – which is totally awesome, because this is such a great timesaver. I tried other solutions but this one is my favorite by far. The API looks cool as well and offers great expendability for coders, so no problem there either.
If your game involves questing, then this is the asset for you. It is easy to use and very powerful.
Be it manual or procedural quest generation, Quest Machine has it covered.