I found the answer.
First we have to kill Grand Master Oberon and take from him The Spatial Warp Almanac .
Next we have to go to Cobra Bastion. We have to go on +2 floor to the kitchen and click on the book there. Next you have to go on +3 floor and than north and enter to the treasury. If you click on skeleton you will get backpack with Key 0303 and Parchment (Writing). Next go south and open doors to the library (use book inside). Finally you can fight with mini boss Gaffir (Boss is located on +3 floor full south of stairs). Next use his body on the fire bowl in his room. You will be moved to a new room. Next click on book on trophy stand and than use The Spatial Warp Almanac in your backpack. You will be moved again and you will receive an achievement "Avid Spectral Reader".