Zadara is a Titan who lives in Sigil, one of the Golden+Lords with unfathomable wealth (and she's a member of the Merkhant sect). She fled to Sigil from the world of Rublia, where she had set herself up as a god until a real god, the greater power Skeartim, chased her off the planet, intending to kill her. Zadara has remained in Sigil ever since.
Zadara is the titan of potential. She has the ability to access others for their potential for greatness. As such, she backs financially those she thinks will be good allies to have on her side, including the rogue Modron Ylem, the Githyanki Djhek'nlarr, the Gehreleth Xideous, Rowan+Darkwood of and the Fated.
She counts herself a rival of Estavan and Shemeshka the Marauder.
Sources:
Uncaged: Faces of Sigil