Complex sentence: She is told by the Seelie Queen she has the ability to create runes that don't exist, but they do, which later enables her to destroy Valentine's ship using the "Open" rune.
Split into simpler sentences: She is told by the Seelie Queen that she has the ability to create runes that don't exist, but they do. This later enables her to destroy Valentine's ship using the "Open" rune.