Legacy of Battle
An ancient summoning circle
The Sentinel Gate is made up of four keystones that serve as the main foci for the summoning circle. Once complete and activated, the Gate allegedly summons raw animate energy and infuses itself into whatever material is provided and the resulting creation serves the summoner completely.
According to Aeron Masrin during Adventure 8 A Rock and A Hard Place, the Sentinel Gate has origins ancient even when he lived in the Kingdom of Imeryd millennia past. It was used by the first king of Imeryd to create an inexhaustible army of stone soldiers and with this army unified the fractured lands of what is now called Ixia as well as the land of the Southern Kingdoms. Before his death, he separated the four keystones of the gate and hid them throughout his realm and told his sons whichever found them and reassembled the gate would be king. Instead, they fought until one remained and the keystones were forgotten.
Aeron also noted that simply possessing all of the keystones was not sufficient to activate the circle as special materials forming the rest of the circle and the correct rituals must be used and known.
During Adventure 4 Spider Webs, Scylda Rast was able to get hold of one of the keystones and using it to try to scry and locate the others.
During Adventure 8 A Rock and A Hard Place, another keystone is located contained within a chamber hidden midst a new marble vein at the Bav quarry.