Q: For the battle scene between Rin and Ilya in the anime, did Ilya just get way stronger?! Was her strength based on 「Fate/Zero」? <UMA>

Nasu: If it's at the land that houses the Holy Grail, then Ilya is indeed that strong. And being able to make a familiar from her hair was in the original draft. The work this time around was especially hard, so I ended up using an "Iri's replacement" approach. By the way, the name of the technique is Elfen Lied [German for Elves' Song, 天使の詩 - Angel's Poem]. The bird's name is Storch Fieseler [German term for a type of plane]. The Ibis that shoots bullets is Zahre (tear), and she can also transform them into an Épée (a sword).
Takeuchi: Woah, that's the first I heard of that.
Nasu: Yea, and it all sounded rather neat when I submitted it. Director Miura can create good results as long as I force everything upon him. Kinoko, remember this.

Fate/Stay Night Animation Material I; Q&A, pg. 40-41