Ennis

Szilard's homunculus, although not his first creation. She was created as his subordinate, and is supposed to have no thoughts or emotion when executing his commands; recently, however, she has been gaining more human emotions, as well as independent thought.

[Spoiler] Eventually, she helps Firo by giving him the necessary knowledge to destroy Szilard and after over fifty years of courtship the two marry. [/Spoiler]

(Source: Wikipedia)