FATE/UNPUBLISHED MATERIAL: TACHIE
Shielder's True Name is Galahad, placed inside the resurrected body of a girl who died in the Fuyuki Fire at the end of the Fourth Holy Grail War. Ernest Gravehill, a necromancer, performs this ritual to help reduce Magical Energy expenditure while summoning Galahad as his Servant.
Shielder initially displays no personality, being like a robot who follows her Master Ernest's instructions. The two personalities of Tachie and Galahad emerge as time progresses, and she becomes increasingly savage as she regains her identity. Tachie's personality switches randomly with Galahad's, making it seem as if she has a double persona. She holds a grudge against Shirou Emiya because she felt that he abandoned her when she called for help in the fire.
In the anime series, Tachie would have died to Gilgamesh after he interrupted a battle between her and Saber. The movie would have ended with Tachie coming to terms with her death and Shirou's survival, and saving Shirou before disappearing.
Known as the Stray Servant, Shielder was a heroine candidate during the development of Fate/stay night who was left unused in the final version. She was considered along with Rider and Caster to be a possible heroine, but she was cut due to the plot beginning to stray so as to keep it manageable for the player.
As Saber is a "Servant of the Sword", she was to be her rival as a Shielder, "Servant of the Shield." She would have been an "abandoned puppy" type heroine who killed her Master during the Fourth Holy Grail War and went on a rampage, surviving into the Fifth Holy Grail War in a similar manner to Gilgamesh.