Character History:
Little is known about Eruka's early history; the basic chain of events she's participated in is more or less covered
on her wiki page. Though it derives primarily from anime canon, it gives a rough idea of what she's been up to for the first story arc.
Personality:
As a witch, Eruka lives for only one thing: destruction. In the world she comes from, that's more than just an unnecessarily dramatic figure of speech. All witches are influenced by the sway of magic, and nothing gives the frog witch greater delight than to get the chance to use any one of her many destructive magical spells. At one point, Eruka even remarks that she's lucky she was born a witch.
Leaving her nature as a witch aside, Eruka herself seems like a perfectly ordinary teenage girl: she laughs, she flirts, and she makes snide jokes at others' expense, and the playfulness she usually reserves for when she's blowing something up gets expressed in slightly less lethal form. When she isn't given a reason to actually put her witchiness on display, she's actually rather normal. It would be a mistake to assume that she is an ordinary girl, of course. Considering the ages witches can live to, it wouldn't be any surprise if she's already past her first century.
There's an immaturity to the way Eruka acts that isn't present in the older witches like Medusa and Arachne, not the least because of her comparative weakness. A rather unusually emotional witch, Eruka often fails to plan for the long term, preferring to act on impulse. This, as it turns out, often has unpleasant consequences. Despite her remarkably poor foresight, she's far from lacking intelligence. Her occasionally neurotic behavior may make it difficult to believe, but Eruka is a clever and competent witch, capable of performing complex magical calculations and spells. She is confident enough in her skills that she has no qualms ordering junior witches to support her while she takes the lead. She's also smart enough to put together the pieces about Medusa's plan to create more Kishin, demon gods formed from a corrupted soul that can inflict madness on those around them.
Around those whose company she feels relatively secure in, another aspect of Eruka's nature emerges: docile, clingy behavior manifests, and she may come to rely (unconsciously or otherwise) on their protection and goodwill. As her relationship with Free proves, she's quite capable of forming these dependent bonds with those who aren't connected to her by magic, including her familiar of sorts, a gigantic tadpole named Jackson. Though it's never explicitly stated, this behavior is probably borne out of an instinctive awareness of her physical vulnerability: many of the other witches have a guardian or a champion of some kind to do the proverbial heavy lifting when push comes to shove, but Eruka has (thus far) failed to command any similar kind of loyalty.
Initially shown as cocky and confident, Eruka's recent history has left her painfully aware of how easily she's outmatched. Forced to serve as the witch Medusa's unwilling lackey (twice-over), she's humiliated a third time when the Meister Black Star captures her and forces her to aid Shibusen, the witches' natural enemy. Though Eruka has a great deal of pride in her abilities as a witch, it's also quickly evident that keeping her dignity intact is less of a priority than keeping herself alive. Eruka certainly has no shame begging for her life when it seems like she might be about to lose it. Cowardly though it may be, the witch has no pretensions of heroism, and there's little doubt that her will to live is strong enough to rival a cockroach's: as long as she can see any way to survive, Eruka will take it.
Abilities:
Eruka is a witch. In Soul Eater canon, this is a quality that one is born with; though abilities can differ between different witches depending on the animal 'theme' they adopt (more on that later) one thing they hold in common is that they are all subject to a force called the 'Sway of Magic.' This is an irresistible instinct to cause destruction wherever they go. This is said not to manifest until a witch has grown older (as in the case of the Chameleon Witch, Angela) and in extremely rare cases, a witch may be free from it entirely (as in the case of Meister Kim Diehl, whose magic powers are not destructive).
While other witches express the desire to cause destruction in less literal means (manipulating people to madness, for example) Eruka is not one of these. She prefers straight-up physical demolition, and the majority of her abilities (accordingly) allow her to perform it.
As with most witches in her world, Eruka's magic revolves around an animal-based theme. In her case, for reasons unknown, she's chosen frogs to pattern her magic after. Her dress and hat, the markings on her face, and even the spells she casts are related to frogs in some way. Her mannerisms display the influence of her chosen theme, because she often punctuates her speech with 'geko,' an onomatopoeia for croaking. It's possibly a side-effect of her ability to transform herself into a frog, or it could be an affectation: it's difficult to say. It only comes out in her speech-- she'd feel a bit silly writing it down, after all.
Her basic abilities are as follows:
Transformation: She can turn into a small, bright green frog. She can still speak in this form, and can manipulate small objects. She can't perform any other magic, however.
Tadpole Bombs: Her main attack. Eruka summons tiny tadpole-shaped bombs which can be timed, or can explode on impact when thrown. Explosion strength varies according to the number of bombs and their size; thus far, the largest she's summoned is large enough to be cupped with her entire hand.
Summoning: She has a familiar, a giant tadpole called Tadpole Jackson. It's capable of flying, handling things with its tail, and usually sees the most use as Eruka's method of transportation. It's also Eruka's BFF, which is pretty sad. Canon doesn't exactly explain how it's summoned, but my best guess is that it's just taken out of some kind of magical 'storage' on Eruka's person, instead of being on a different place. In that case, it functions more like a pet-- though it has a limited intelligence.
Arithmetic/Magical Calculation: The only non-frog related ability she's displayed thus far (though her chanting relies on frog-related words). It appears to have a variety of purposes, but its main one is to allow a large or complicated spell to be more accurately cast, or to stabilize one in progress. It seems to be a support ability rather than an aggressive one, given that it requires concentration and time to set up.
Since she has a recurring appearance in canon, this list of abilities may be added to as necessary.