There are classification of Mara. Four Mara (Skt. catvāri māra) :
- the mara of the aggregates (Skt. skandhamāra; Tib. ཕུང་པོའི་བདུད་, Wyl. phung po’i bdud), which symbolizes our clinging to forms, perceptions, and mental states as ‘real’;
- the mara of the destructive emotions (Skt. kleśamāra; Tib. ཉོན་མོངས་ཀྱི་བདུད་, Wyl. nyon mongs kyi bdud), which symbolizes our addiction to habitual patterns of negative emotion;
- the mara of the Lord of Death (Skt. mṛtyumāra; Tib. འཆི་བདག་གི་བདུད་, Wyl. 'chi bdag gi bdud), which symbolizes both death itself, which cuts short our precious human birth, and also our fear of change, impermanence, and death; and
- the mara of the sons of the gods (Skt. devaputramāra; Tib. ལྷའི་བུའི་བདུད་, Wyl. lha’i bu’i bdud), which symbolizes our craving for pleasure, convenience, and ‘peace’.
That number 4, Devaputra Mara, is sometimes said to be a real being, dwelling in Paranimittavasavati - Indeed his other name is Vasavati Mara. In chinese translation, he is called “Demon King of the Sixth Heaven” - because Paranimittavasavati is the sixth heaven.
Honestly, I am not sure about if this being is real, or just methaphor.
Lord of Death. There is a version of the story where Yama means realm of the dead, and King of the Dead is Yamaraja. Sometimes it is said that this being is the one judging our karma. In Chinese folk religion, this figure become Yan Lo Wang / King of Hell, the one judging and giving punishment.
How does one end up as Yamaraja, or maybe, Hell’s Guards who execute punishment to Hell beings? (They are the same as they are having a job). Also, is it good karma or bad karma?
Well, citing Vasubandhu,
In an intriguing example, Vasubandhu argues that the torturing guards in hell are not real beings but communal projections by hell denizens with which they torture themselves, since it is illogical that one would be born into hell unless one deserved it based on one’s previous actions, and if so, then one would not be immune to hell’s tortures–but the guards don’t suffer, they mete out suffering. The implication of his argument is that hell itself is merely a paranoid projection. Vasubandhu
So, his argument is that, that Lord of Death as the one judging beings’ deeds is not real, but just projection of the mind. This solve the problem of what kind of karma Lord of Death may have.