Question

What was nagin nagini plants and why did they make the planet?

Answer 1

One thing we know for sure about Horcruxes is that they must have many powerful spells upon them to protect them from harm (consider how they were unable to damage the locket).

People have often wondered what kind of snake Nagini is, given that she is so very large and strong and that she has an unusual kind of venom (according to Arthur's report of the St Mungo's Healers' opinions). I like to think that Voldemort found a normal snake and transformed her to make her the most dangerous snake in the world, rather than her being of a magical species unknown to us muggles.