Mara's Servants
Where would a demon be without her faithful (*cough*) and loyal (*cough*) servants? Mara commands a variety of servants in the course of the manga, some more useful than others, some more loyal than others. She also seems to have a strange affinity for rats... Well, at least the rats are more reliable than the octopi. Here is a list of Mara's servants, many of which she creates herself, being the always resourceful and reliably short-sighted demon that she is.
Spy Demon.
A bizarre combination between a video camera and some sort of flying imp, the spy demon records audio and visual data that Mara later "downloads" by sticking its tail into her ear. The spy demon possesses intelligence and the power of speech; in addition, it seems to be the only one of Mara's servants that is completely obedient and loyal to her.
Booster Demons.
Mara creates five of these squid-like booster demons in order to help her slip some poisoned chocolate to Keiichi on Valentine's Day. The booster demons can speak and have minds of their own, although they are really quite stupid. Mara uses the booster demons not only to do sneaky errands for her (such as switching Belldandy's chocolate heart with a poisoned chocolate heart that Mara made), but also to form a shield around her that protects her from Belldandy's powers. Unfortunately, after the booster demons accidentally eat a chocolate heart filled with one of Urd's love potions, and then eat the poisoned chocolate heart that Mara filled with a factor-reversing potion, they became "good", suddenly filled with the urge to repent for the misdeeds they have done. The booster demons turn against Mara and decide to help Belldandy instead.
Senbei.
A self-titled "God of Poverty and Destruction," Senbei is actually a tiny genie who lives inside what looks like a Ramune Soda bottle. He has the power to manipulate the Law of Conservation of Happiness, which means that he raises his own level of happiness by bringing misfortune to others. He locks onto the targets (victims) that Mara orders him to, and brings bad luck upon them, causing them to become unhappy. Senbei acts as Mara's right-hand man in several chapters, including during the Devil Urd story arc. Even though he is loyal to Mara, he resents the fact that she insults his abilities (retaliating once by striking her with a lightning bolt), and furthermore, he is not hesitant to point out holes in her sometimes loony plans. In chapter 60, it is revealed that Senbei also has the power to bring good luck upon others, although doing so makes his own personal happiness level go down.
Rats.
In chapter 139, Mara is seen hanging out with some rats in a deserted video game arcade. The rats wear lab coats and look like scientists. One says to Mara, "The item you wished for is completed!" in reference to the Soujinki, which would seem to imply that the rats built it. Other than that, one rat fetches the Soujinki for Mara when she orders it to, and that's the last that we see of the rats. Incidentally, the rat with the eye patch looks almost exactly like one of the rebel rats that Mara commands in the Mini-Goddess anime. Knowing Fujishima, that's probably a deliberate reference.
Mini Ninja (Kodama, Hikari, Nozomi, and others).
(Note: Kodama, Nozomi, and Hikari are also the names of the three shinkansen, or bullet train, lines in Japan.) Inspired by a description on the box of a ninja movie video, Mara creates a virtual horde of miniature ninja as her "greatest warriors" to use against the Goddesses. The first two ninja, Kodama and Hikari, begin life as simple rats that Mara transforms into (tiny) human ninja, granting them the gifts of intelligence, speech, and exceptional fighting skills. First Mara creates Kodama, the "Mistress of Illusion," and sends her out with the mission to sow the seeds of mistrust amongst the Goddesses. When Kodama fails in her mission and decides to side with Belldandy instead, Mara sends out Hikari to hunt down Kodama. When Hikari is unable to kill her closest friend and also fails in her mission, Nozomi of Senrigan (senrigan meaning "second sight" or "clairvoyancy") is sent after them both, along with an entire horde of tiny, masked ninja that overrun the Morisato residence. Belldandy uses a powerful spell to stun all the ninja, and then Urd convinces the ninja that if they all defect from their clan, they can stop fighting each other. The ninja write Mara a curt note telling her that they are leaving her clan, and then are never seen again.