Psiren, whose real name is Clara, is a cat burglar who publicizes her crimes so that her sinking city Aquroya (pronounced "Ah-croy-ya"), an analogue of Venice, will be full of life before it eventually disappears beneath a lake. Her alchemy utilizes cards and water and her transmutation circle is on her chest. She uses this to her advantage when battling men by slowly unzipping her shirt and then using alchemy against them. Known as a great beauty, she was Ed's first female opponent, which is pretty obvious when he tackled her on a roof as he accidentally grabbed her left breast with his automail hand. Psiren/Clara also took advantage of Al's gullibility by claiming she was stealing to save a hospital, a convent, and a school all while disguised as a nurse, nun, and schoolteacher respectively. She shows an affinity towards Edward, possibly romantic, even as he finally captures her, going so far as to offer to steal anything he wanted. When they part ways, she tells him to go to Xenotime for more information on the Philosopher's Stone. After she is arrested, she easily escapes an hour later.

Neither Psiren nor Clara make an appearance in the manga.