In the book the alchemyst, what is missing in the codex?

The pages are the Final Summoning, needed by him to return his masters, the Dark Elders, to earth ... and so begins a fast-paced race as Dee pursues the twins and Nicholas for the pages of the Codex, whilst Nicholas aided by Scathach and others race to get the twins' latent magical auras awakened, to get them schooled in the use of the elemental magics-Water, Fire, Earth, Air, and Aether – and to rescue his wife, Perry. That is what I managed to find for you. You may also check it with the help of online writing service and let them analyze this book. Turn to the professional service I use  quite often.