QUOTE
Listen to me while I tell the tale of your lovers. There was Tammuz, the lover of your youth, for him you decreed wailing, year after year. You loved the many-coloured roller, but still you struck and broke his wing [...] You have loved the lion tremendous in strength: seven pits you dug for him, and seven. You have loved the stallion magnificent in battle, and for him you decreed the whip and spur and a thong [...] You have loved the shepherd of the flock; he made meal-cake for you day after day, he killed kids for your sake. You struck and turned him into a wolf; now his own herd-boys chase him away, his own hounds worry his flanks.
Ishtar, Assyrian and Babylonian goddess of Love, Sex, Fertility, and War.
She isn't the goddess of War so much because she kicks ass (though she can when she's angry) but because she tends to start them.
She has wide-ranging sexual tastes and an insatiable appetite that leads her to many lovers of all sorts, gods and mortals, two-legged and four. She tires of them quickly and tosses them away like so much garbage, often in a manner that leaves them irreparably destroyed, because she's sort of a sadist, and a very creative one.
She is extremely manipulative. When she wants something, she resorts to bribery, trickery, and outright threats to get her way. Often, what she wants is to screw over someone who jilted her, or whom she merely tired of. More than once, she went so far as to threaten to tear open the gates of the underworld with her bare hands and raise an army of the dead to eat the living in order to get her way. Though she never followed through with this threat, it is apparent that some rather powerful deities assumed her to be capable of the feat, because they caved rather than risking it.
Ishtar's cult was known for sacred prostitution, which not particularly uncommon when dealing with love goddesses. In fact, she has an entire holy city, Erech, dedicated to the practice. It was sort of like the Vatican, only with a lot more sex.
Voodoo, Black Magic. Come on now, go with a Babylonian or Assyrian tradition. Have her use Ishtar as a Mentor.
I'm also going to say that a Possession tradition is a bad idea for a beginner, and an especially worse idea for a beginner and a new GM. There are technical issues that can make Possession either absurdly underpowered or absurdly overpowered depending on how it is played, and if the GM implements all the rules correctly.