On the subject of Mara, here is something that may pique some interest...
In Brahmanimantanika Sutta (MN 49) there is a particularly interesting interaction between the Buddha and Mara in the retinue of Baka the Brahma. The Buddha appeared in the Brahma realm after perceiving the pernicious view of eternalism that was taking hold in Baku's mind.
On the meeting between Buddha and Baka, Baka says:
'Come, good sir! Welcome, good sir! It is long, good sir, since you found an opportunity to come here. Now, good sir, this is permanent, this is everlasting, this is eternal, this is total, this is not subject to pass away; for this is where one is neither born nor ages nor dies nor passes away nor reappears, and beyond this there is no escape'
4 When this was said, I told Baka the Brahma: 'The worthy Baka the Brahma has lapsed into ignorance; he has lapsed into ignorance in that he says of the impermanent that it is permanent, of the transient that it is everlasting, of the non-eternal that it is eternal, of the incomplete that it is total, of what is subject to pass away that it is not subject to pass away, of where one is born, ages, dies, passes away, and reappears, that here one is neither born nor ages nor passes away nor reappears, and when there is an escape beyond this, he says there is no escape beyond this'
Then, something interesting happens...
5. 'Then Mara the Evil One took possession of a member of the Brahma's Assembly and he told me: 'Bhikkhu, bhikkhu, do not disparage him, do not siparage him, for this Brahma is the Great Brahma, the Overlord, the Untranscended, of Infallible Vision, Wielder of Mastery, Lord Maker and Creator, Most High Providence, Master and Father of those that are and ever can be. Before your time Bhikkhu, there were recluses and brahmins in the world who condemned earth...
...Be sure, good sir, to d only as the Beahma says; never overstep the word of the Brahma. If you overstep the word of athe Brahma, bhikkhu, then like a man trying to deflect an approaching beam of light with a stick, or like a man losing his hold on the earth with his hands and feet as he slips into a deep chasm, so it will befall you, bhikkhu. Be sure, good sir, to do only as the Brahma says; never overstep the word of the Brahma. Do you not see the Brahma's Assembly seated here, bhikkhu?' And Mara the evil One thus called to witness the Brahma's Assembly.
It would appear that Mara, instead of confronting the Buddha head-on, was trying to entice the Buddha to ensure that Baka the Brahma remained in the fools paradise of eternalism. The commentarial explanation referenced in Bhikkhu Bodhi's note to paragraph 5 reads:
MA Mara's intention is to show: 'If you do as a Brahma says without overstepping his word, you too will shine with the same splendour and glory as that with which the Brahma's Assembly shines'
Then the story thickens...
The Buddha says:
When this was said, I told Mara the Evil One: 'I know you, Evil One. Do not think "He does not know me". You are Mara, Evil One, and the Brahma and the Brahma's Assembly and the members of the Brahma's Assembly have all fallen into your hands, they have all fallen into your power. You, Evil One, think: "This one too has fallen into my hands, he too has fallen into my power"; but I have not fallen into your hands, Evil One, I have not fallen into your power
After that, Baku and the Buddha engage in dialogue to see who is more powerful.
12-23 "Brahma, having directly known water as water,...fire as fire...air as air...beings as beings...gods as gods...Pajapati as Pajapati...Brahma as Brahma...the gods of Streaming Radiance as the gods of Streaming Radiance...the gods of Refulgent Glory as the gods of Refulgent Glory...the gods of Great Fruit as the gods of Great Fruit...the Overlord as the Overlord...all is all, and having directly known that which is not commensurate with the allness of all, I did not claim to be all, I did not claim to be apart from all, I did not claim all to be 'mine', I did not affirm all. Thus Brahma, in regard to direct knowledge, I do not stand merely at the same level as you, how could I know less? Rather, I know more than you.'
This exchange was followed up by a display of supernormal power during a contest whereupon the Buddha vanished from the Brahma's gaze but the Brahma could not vanish from the Buddha's gaze.
Brahma and his Assembly were suitably impresed. But then...
29 Then Mara the Evil One took possession of a member of the Brahma's Assembly, and he said to me: 'Good sir, if that is what you know, if that is what you have discovered, do not guide your [lay] disciples or those gone forth, do not teach the Dhamma to your [lay] disciples or to those gone forth, create no yearning in your [lay] disciples or in those gone forth.
Here again, Mara tries to dissuade the Buddha from teaching the path that leads one out of misery with the paltry incentive that after death, the enlightened one will be established in 'a superior body'. The Buddha then rebukes Mara and outlines that the Tathagata has abandoned all the taints that defile and is not subject to future arisings, and that the nature of the Tathagata is that he will teach the Dhamma out of compassion, unlike the motivation of Mara.
What many Theravadins hold is that Mara is a real being who lives in the deva realm, but Mara is also used as a metaphor for one's defilements. My view is that both positions are relevant and neither are mutually exclusive of the other.