The way they are used/obtaining the rights for the Gods&sacred beasts

The monster or monsters can fight along side. they only fight when the feel danger or their summoner is dying or injured. Uchihas can be saved only when they are near death and have earned the sharingan. A monster can help a student but only when the summoner is outnumbered. Kuriboh can multiply by calling out Mutliply,Kuriboh, Winged Kuriboh can go to its Lv 9 or 10 form only from sensing goodness within the heart of the summoner.

The Egyptian gods Chose there summoner on their own. The Sacred Beasts will do the same. Exodia will be chosen to the most intelligent. Including its Necross and its other form.