The Queen Trap is a dungeon that is part of Sarah's Throne. Like the rest of the throne, it was presumably built by Edd as an accessory to the throne. Originally, it was used by Sarah to entrap Eddy when he tried to leave in the middle of Sarah's games. However, Eddy later turned the tables on Sarah by taking over her throne, and when she complained, he used the dungeon to seal his victory and trap her.
The Queen Trap appears to be very simple, as it is just a crib with a rope attached for appropriate dropping. Despite its simple construction, it seems to be quite strong, as it was able to hold back both Eddy and Sarah.