K so far the tips ive seen are the following: nessa is warmth related, it is acquired by doing something similar to the inverse of tama, it is not normally something you'd do it a run, and it doesn't require items, (Not sure if this includes cheese for tama egg), I am taking some guesses, but maybe an egg needs to be hatched in the volcano area, or the egg has to be a pyris egg (for heat), but these both seem like things you would normally do in a run
The Mamu seemed pretty easy to get, I just really over complicated it, so I'm probably going to figure out that I'm also over complicating nessa a bunch