Siebe (or anyone else): Do you know the name of sutta which describes how Devaputta Māra once got inside Ven. Moggallana’s body? He then admonished the Māra and reminded him that he himself was the Māra at an earlier time, and had to be born in the apayas by insulting a Buddha at that time.
The point is that Māra himself would die one day and can be born in the apayas. There is no realm in this world of 31 realms that is “safe”.