|You've set up an intriguing world and some nice characters. Peri is quite convincing as a confused, scared kid. Besides having a cool name, Crepuscula looks to be a quality villain. The dialog between Shea and Crepuscula does a great job of hinting at the issues between them, which I assume will be explored in future chapters.
The end really stood out. While certainly foreshadowed, Shea's murder comes up suddenly and with great impact. Your descriptions throughout were quite vivid and they really shined in the last few paragraphs. The last two lines were very effective and created a strong image for me.
Suggestion-wise, you may want to cut back on the number of pronouns. Especially in the first few paragraphs, there were several points where I lost track of who was doing what. Also, there are some spots where it's unclear how Peri knows something. For instance, if Crepu has a youthful appearance, how can Peri tell that her mother and Crepu are the same age?
You have a great start to a story here. Keep it going.