How did Alluka Zoldyck obtain her powers? Due to some recent news about the Hunter x Hunter manga being continued, I decided to re-watch the anime and some question popped into my head. I haven't finished it yet, but I don't remember any explanation of the origin of Alluka's power the first time I watched it.

I've watched some videos but they don't really explain my question. I also couldn't find an answer here.

Was the origin of Alluka's power ever explained in the anime or perhaps in the manga?
It has been confirmed that Nanika came from the Dark Continent and evidence suggests that Nanika is Ai, the desire of co-dependence.

As to how Nanika started possessing Alluka, we don't know for sure but seeing how Zigg Zoldyck went to the Dark Continent, it is possible he brought it back to the outside world.