From the back of the book:
"Many are the stories of this creature's ferocity and unbridled power. Now, take a look inside the alien world of one of the most feared monsters in the AD&D game in this visually stunning 96-page accessory. I, Tyrant contains information on all beholders and beholder-kin including: detailed explanations of their deadly eye powers; an insight into beholder psychology; an explanation of the creatures' social organization; new magical items created specifically for beholders; and other useful game information on these deadly denizens of the planes. I, Tyrant also comes with a poster that details in full color many known beholder types.
This lavishly illustrated book is the first in a new series of accessories that focuses on some of the most popular monsters in the game. DMs and players alike will find this Monstrous Arcana (TM) accessory highly useful when playing Eye of Pain, Eye of Doom, and Eye to Eye a trilogy of adventures centered around beholders."