It is not known if "The Mother" is a variation of the Siren strain, or if it is an entirely new Chimera. It is located inside the Birthing Chamber of the Chrysalis Lair. Near the final boss battle with The Chrysalis, James Grayson has to fight this creature.
The Mother uses similar sonic attacks used by Sirens, but also has the ability to suck the player towards it. During this special attack, if the proper button combination is not pressed correctly, it will proceed to consume Grayson and throw whatever left of him away.
Although the entire battle takes place in a underwater breathable liquid; similar to the liquid Raine Bouchard was kept in Bonn. This boss shows weakness to any of the BM003 Razor's attacks and other energy weapons that function underwater.