I - Rules
(see RTL, p. 6, 24)
In the Advanced Campaign, monsters are divided into three categories: Humanoid, Beast, and Eldritch. Each monster’s category is indicated by the icon in the upper right corner of its monster reference card.
The strongest avatars for eldritch monsters are: The Demon Prince, The Sorcerer King.
II - References
Below is the average for all eldritch monsters (normal and master, copper, silver, gold and diamond).