Morgan le Fay is a sorceress, originally a woman called Lilith from the earliest ages of humanity, and the primary antagonist of the Oracles of Fire series (although the readers retroactively discover that she was behind most of Devin's actions in the first series). She cannot take something unless it is willingly given to her (this apparently does not include lives).
Morgan's evil schemes have been in motion since the very earliest moments of the saga, when she managed to obtain a place on Noah's ark by coercing her sister Naamah to marry Noah's son Ham, and turning herself into a wraith, taking the form of a bird. She sets in motion the birth of the first Naphil, recruits King Nimrod's son Mardon to raise an army of Nephilim and a host of slaves (the underborns) via genetic engineering. She is able to grow a tree of life in her underground chambers. After Mardon's efforts produced the two Oracles of Fire (Acacia and Mardon's protégé, Mara) spoken of in Enoch's prophecies, she manages to execute one by tricking the other into a betrayal. Even after Babel is destroyed and her attempts to kill Mara (now renamed Sapphira Adi) are foiled by Elam, who double-crosses Morgan instead of Sapphira, she continues plotting.
Eventually she ingratiates herself with King Arthur until she is revealed to be evil by the prophet Merlin, becoming the Morgan le Fay of legend; and builds the fanatical knight Devin into a supernaturally powerful dragon slayer, thus setting in motion the events of much of the Dragons In Our Midst series.