It liked to think of itself as rather smart. At the very least it knew it was smarter then the older models. The Lancer was the future of Little Sister protection, and it was ready for that future!

Well, as ready as it was for the future, it was inversely ready for the Alpha that tore it a new one and killed it's daughter. With failure on its mind, it accepted whatever afterlife it would be given...

Only... it was given an offer. Accepting it would bring the creation of Rapture and the Little Sister it failed together again. If it declined the offer and she would just get another Big Daddy. The answer was clear to it. Now it is reprogrammed, rebuilt and resented, but it still has one purpose. Even if the world was unlike anything it had ever known, it was fully ready to dig in and hold back anything that came for its daughter.

It was her Big Daddy, she was it- his daughter!