As far as I know the only way to get "Hel" is Atlantis pull. Is that right?
Does she appear in Atlantis pull every time? or time to time, randomly?
Hel is an old Hero of the month
Yes, currently the only way to pull her is from Atlantis pull, but she is not always available. Every month, two different old Heroes of the Month return and are able to be pulled. You can check the Atlantis page for more details.
What do you think?