Castlekeep Ruins

The Old Castlekeep of Daventry is a set of ruins in Daventry. It is located on the foothill of a small mountain near Connor's Village. It is surrounded on one side by a moat, and is the ruins of a castle that predates Castle Daventry, Edward's castle, the castle that Graham and Valanice currently live in.

The castle keep ruins are protected by traps, to protect a strange magical device (a magical teleportation circle) hidden within its walls. A chest filled with treasure could be found hidden behind a strange magical false wall. A hero of Daventry from long ago is buried in a tomb near the moat. During the great cataclysm it was taken over by Spriggans, including their leader. One of Daventry's citizens was in the keep at the time of the the cataclysm and was turned to stone by the vile tempest. A strange magical device is located in the keep, and could be used to travel between locations in other lands by use of a Magic Map.

Behind the scenes
According to Mark Seibert, MOE producer, the old castle keep are the ruins of a castle that predates the Castle Daventry from the previous games, and the Castle Daventry in the game was intended to be the same one seen throughout the series, even though its location and physical design is inconsistent with all other sources.

Unrelated, but interesting is in the 1st and 2nd Edition, of King's Quest Companion, the An Encylopedia of Daventry talks about secret passages that pass under Castle Daventry, Edward's castle, that lead to portals that lead to other parts of the world. This is somewhat similar to the portal idea in the secret passage inside the Old Castle Keep.