Anima is the aeon whose fayth is Seymour's mother. The name is derived from psychology definition: "The feminine inner personality". Seymour's mother became a fayth to imbue Seymour with the power to summon Anima as moral support and comfort for him. Anima's power only made Seymour more power-hungry which shows a lot of neglect for all the pain his mother suffers for him. The fact that anima cries drops of blood is a harsh representation of this. The fact that the aeon is "chained up and bound" is sort of symbolic of the way Seymour treats the memory and trace of her. Locked up for use at his will.