At this time, Abbot Marquard I of Fulda secured the abbey estates and built castles that were visible from a long way as a sign of his influence.

In this document the Archbishop of Mainz, Siegfried III, also the overseer of Fulda Abbey, guaranteed to Count Palatine Otto II the arrangement agreed in the previous year, the details of which are unknown.

In the early 14th century, the resources of Fulda Abbey ran out so, in 1332, Prince-Abbot Henry VI of Hohenberg enfeoffed Otzberg Castle and the Fulda part of Umstadt for 4,600 pounds of Heller to Werner of Anevelt and Engelhard of Franckenstein, who carried out building work at Otzberg to the tune of 200 pounds.

In 1390 the abbey sold Otzberg and Hering and the half of Umstadt with the Hanau fief, which had meanwhile increased in value to 33,000 guilders, to Count Palatine Rupert II.

In the dispute over the Landshut succession, Emperor Maximilian imposed the imperial ban on Count Palatine Philip for a breach of the Landfrieden.

In 1621, during the Thirty Years' War, a Bavarian corps of 2,000 men and imperial and Spanish troops camped in the area of Otzberg-Umstadt and besieged Otzberg Castle.

The castle and amt of Otzberg as well as half of Umstadt went back to Hesse in 1623 as compensation for war damage suffered.

From 1711 active service soldiers were gradually replaced by disabled veterans, so that from 1720 the castle became purely an invalids' garrison that guarded the prisoners incarcerated there.

In 1985, a museum the Collection of Folk Art in Hesse (Sammlung zur Volkskunde in Hessen) moved into the Bandhaus.

The appearance of the fortress is dominated by its double concentric walls built in the 16th century and oval in shape, and the bergfried which is of Romanesque origin.

The bergfried, also known locally as the Weiße Rübe ("White Beet", also the name for the wild turnip), is the oldest building in the castle.