Skeleton Isle Prison

This is a prison for the City of Ansbridge where people are taken to either serve their sentences or to await being put to death.
The island is an outcropping of sharp obsidian rocks that stick up in jagged angles. It has been likened to a pile of nails dropped on a bed of broken glass. It is notable that the shoreline for the rest of the bay is sandy and no sign of obsidian elsewhere. A path has been made from one of the more approachable portions of the island, leading to a large tower. Armed guards, both with crossbows and with magic, patrol the upper decks of the tower. They are one line of defense, but the island itself is the bigger deterrent.
Few people attempt to escape the island, partly because of the security measures inside, others because of the dangerous rocks. Prisoners are kept without shoes, and one step off the path and the gravel/sand will slice into their flesh. The same surrounds the island, making the shallow dock-area dangerous without a boat. Needless to say, no boats are kept on the island, only arriving to transport prisoners or guards and leaving just as soon. Lastly, the guards that surround the island are instructed to make no attempts to re-capture escapees, but to always use lethal force. The corpse is examined to ensure they are dead, and then left where they lay. It is believed that this is the reason it has gotten the name Skeleton Isle.