Little is known about this summoning circle except it have been a legend for 1000 years. Rumors has it. That whomever posses the Book of Death could open a portal to the land of the undead and control anyone who enters through the portal. Only a summoner with great skills and the right
ingredients would be able to open the portal.

The Circle would not work as a regular circle. But it would change into dimensional rift and change the whole place it is located in. Everything near the circle would start changing to undead. Even living plants and creatures would change and turn in the presence of the circle. The circle would feed on the living and in the end nothing will be alive.

Master Scholars and governments that new about the circle would try to hide it from the rest of the world since the circles powers was to immense to handle for any man of magic. And no one should be able to have that much power. Evil summoners have in decades tried to find the circle, but without any luck.

If the Book of Death would ever bee found. World orders, undead hunters and heroes would flock to it and try to destroy it. The book itself is said to be indestructible, but three ancient magic wisdom’s should be able to hide, reduce its power and close the circle. 

History (Rumors)

– The Circle was first used in the world during the time of thousands magics when a Elven warlord tried to conquer the world with it. The plan didn’t go as intended and the army of dead turned on the Elven Warlord. 
– The second time the circle was active was during the Elf Dwarf war. One Elven ruler gave the Book of Death as a gift to a Dwarven ruler. Little did the dwarven ruler know that this was not a token of respect but rather a genocide to be. The Circle of Death was activated inside a Dwarven complex and destroyed a critical dwarven stronghold. But the book was lost for some time. 
– The book was never activated again. But a sect of undead hunters found the book and kept hold of it for many years. One day the book was gone from the keeping. Some say it was with intention the book was lost. The sect searched for the book in many years but it was not found. It was finally lost to the world and never to bee seen again.