The Mission
If Mara really is just a working girl trying to do her job, then what exactly is her job? Being a demon, Mara does not just ascend to Earth for no reason. Mara continues to stay on Earth because she is trying to accomplish a specific mission. However, just exactly what that mission is, and what Mara's ultimate goals are, change and evolve as the manga series progresses.
In the beginning, Mara's job is nothing more than to be an antagonistic troublemaker.
"Far be it from Mara, top agent of the Demon Office, to let these Goddesses do as they please!... After all, my job is to make trouble for you two!"
~ Mara, chapter 26.
In the early volumes of manga, Mara's only real goal seems to be to make Belldandy miserable. In order to accomplish this, she begins by targeting Keiichi, and turning him into a lizard. Next she goes on to bring a whole slew of troubles upon the Goddesses, including trying to help Sayoko seduce Keiichi, turning Megumi into a car, trying to feed Keiichi poison chocolate on Valentine's Day, awakening the Lord of Terror, possesing Megumi, and unleashing Senbei (the unhappiness genie) upon Keiichi and Belldandy. "Let Belldandy taste the sufferings of hell!" she thinks to herself in chapter 45. It's pretty obvious at this point in the manga that what Mara desires most is to watch Belldandy suffer.
However, later in the manga, it becomes clear that Mara has another mission to fulfill while on Earth. In addition, her goals change regarding Belldandy. At first, Mara just wants Belldandy to be unhappy. But later, Mara begins to focus more on finding ways to make Belldandy return to Heaven. Unfortunately, most of Mara's plots to force Belldandy to leave Earth still involve making Belldandy suffer one way or another.
"And what's the point of sealing up Belldandy? I'm not out to trap the Goddesses, you know. I'm here on Earth to track down people who've recieved blessings from them, and to give those people a chance to sign pacts with us demons instead. My job is to expand our market share, period. Frankly, I'd be happy if the Goddesses packed up and went home. I mean, it's highly unusual for us to stay here this long!"
~ Mara to Demon Urd, chapter 62.
Mara first plans to use Demon Urd to seduce Keiichi and break Belldandy's heart, hoping that Belldandy will then leave him forever. (Actually, Urd gave her that idea, but whatever...) Mara is visibly upset when Demon Urd wants to seal up the Goddesses instead, and she only agrees to go along with Demon Urd's plan when Demon Urd promises that she can remove the seals later. This is the first time Mara admits that she wants the Goddesses to go away, but she doesn't actually want to hurt them. Well, that is, she doesn't want to hurt them *that* much (she still wants to break Belldandy's heart).
Now, the quoted passage above comes from the Studeo Proteus translations, but the dialouge in the Japanese original is slightly different. Mara originally mentions:
"To improve my standing within Hell is my goal."
~ Mara to Demon Urd, chapter 62.
The idea of improving her rank in Hell is central to Mara's motivations in the later chapters when she works beside Hild. However, what exactly she needs to do to improve her rank does not become clear until later, either. The way that she says it in the context of chapter 62, it sounds like Mara improves her rank by offering contracts to humans. However, much later in the manga (see below), Mara makes it sound as though she can only improve her rank by getting rid of the Goddesses.
After the Demon Urd fiasco, Mara doesn't show up again until chapter 81, when she hears Sayoko's wish to be crowned the Campus Queen of Nekomi Tech. Mara grants Sayoko's wish, and in doing so sets up an elaborate trap which eventually forces Belldandy into a very comprimising position.
"I... I did it! I really did it!! I defeated Belldandy! Finally! FINALLY I can go home!!"
~ Mara, after Sayoko tells Belldandy to "go home," chapter 85.
Mara's line here is slightly different in the Japanese original, where she says "I'll finally be at peace," although the idea is the same. Although it seems as though Mara came to Earth of her own free will, she may not be able to return to Hell until she has defeated the Goddesses, and thus improved her ranking down Below.
Yes, it finally becomes clear later. The primary thing that Mara needs to do in order to improve her ranking is to defeat Belldandy (and/or the other Goddesses). And by "defeat", it probably means that Mara needs to get the Goddesses to leave Earth - either by returning them to Heaven, swallowing them up with the soujinki, or whatever. (We know that Mara can't possibly intend to *kill* the Goddesses, because the Doublet System prevents that.)
"The Goddesses who have kept me from improving my rank... with one swipe I can take them all out!"
~ Mara bragging about her latest plot, to Hild, chapter 139.
So much for Mara's supposed mission of offering contracts to humans. At this point in the manga, Mara seems to have thrown the idea of contracts out the window. She is focused solely and only upon getting rid of the Goddesses; in addition, Hild seems to endorse the idea that this is all that Mara needs in order to improve her ranking in Hell.
Thus, to summarize: Mara's motivations, and her central mission as an agent of the Demon Office, are often murky and do change as the manga series progresses. Mara first appears on Earth because, in her own words, she doesn't want Belldandy to be able to do as she pleases. She seeks to make Belldandy miserable solely for the sake of making Belldandy miserable. Mara later mentions that her primary mission on Earth is to offer contracts with humans that compete with the "market share" of the Goddess Relief Office, and eventually, she does sign a contract with one human - Sayoko. However, as the manga continues onward, Mara pays little to no attention to contracts ever again. By the time that Hild comes calling, Mara says that in order to improve her ranking in Hell (which is now her central focus), what she needs to do is to defeat the Goddesses, plain and simple. So, it's back to square one, in a sense. Although at least this time, Mara has a self-serving motivation (to improve her own ranking) when she troubles Belldandy, instead of just no motivation at all (causing trouble for the sake of causing trouble, as she did in the beginning).
