Cogsley (Kuggson in Swedish) was an assistant of Silas Charnon (the great grandfather of Emily and Navin) and a supporting character of Amulet. At the start he was very skeptical about serving Emily and Navin, because of their age.
Vigo mentions that Cogsley is a old model of his robot. In fact, Cogsley he built the house together with his master, Silas Charnon. Cogsley is very emotionally attatched to the house.
In Book 4, The Last Council, he and Miskit were carried to a wyvern’s nest. He was pushed by Miskit and smashed a wyvern egg. Then came out a baby wyvern, thinking Cogsley was his mother. In the first book, Cogsley was mean to Emily and Navin but soon afterwards he started getting attached to them.