She is the leader of her kind, referring to them as her brood. However, she was captured by the Beastlords of Mardin, and was used by them to gain control over the deathclaws. She was liberated by the Warrior of the Brotherhood of Steel. Thankful, she permitted some of her kind to join the Brotherhood, and even joined it herself.
Mother becomes available after the Warrior reaches the rank of Junior Knight, and after he/she helps her in Mardin.
"Have you come to kill me? Sssurly you wissssh to kill the ssssource of the DeathClaw infesssstation? Kill me and allow my young a chancsse at freedom. I cannot live another day knowing I am the very collar that holdsss my children in bondage. You hesitate. Maybe there is another anssswer. Maybe you can ssset me free and allow a mother's vengeancsse. Free me and I will bathe in their leader's blood and feast on his hot, quivering flesh."
"You fight as if you were from my own brood, warrior. Hsst! My children are now free due to your ssselflessss act. Thank you for your trussst. I have much to think about. I would ssspeak with your leadersss, after I have gathered my brood around me."
"(nods to you) Your eldersss are wissse, warrior. They acsssept my brood as recruitsss. My children wishhh to ssshow their thankssss. It isss ssstrange time no? My young fighting with you and the ressst of the sssoft hairless onessss. Treat them well and don't feed them flesssh after midnight. Farewell." – Mother at Bunker Gamma
Mother appears only in Fallout Tactics.
Her appearance is different in the various settings where she is encountered:
In Mardin she appears with pure white fur and is labelled as "Matriarch".
In Bunker Gamma she appears with pale gray fur and is labelled as "Matriarch" as she runs around the garage area.
When recruited into the party she appears with dark gray fur and is labelled as "Mother". It is done, probably, to distinguish two separately-programmed models that made up this character: a recruit and quest-important character.
Behind the scenes
The following is based on unverified behind the scenes information and is speculative and may not be accurate.
When the elders accept her children as recruits for the Brotherhood, Mother will warn the Warrior not to feed them flesh after midnight. This is a reference to the 1984 movie Gremlins, in which giving the mogwai food after midnight will turn them into the murderous, reptilian gremlins. This is also likely a comment on the mammalian appearance of the deathclaws in Fallout Tactics, as opposed to their reptilian counterparts in the other games.
End of information based on unverified behind the scenes information.
If you recruit the Mother, then choose the perk Mutate! to replace one of her traits, she will actually lose it but the replaced trait won't appear.
↑Mother: "Your eldersss are wissse, warrior. They acsssept my brood as recruitsss. My children wishhh to ssshow their thankssss. It isss ssstrange time no? My young fighting with you and the ressst of the sssoft hairless onessss. Treat them well and don't feed them flesssh after midnight. Farewell." (Mother's dialogue)