Baron Othrok was a Baron of Dwynnen, who ruled the area in the middle of the Third Era. Although the Baron definitely existed, it is difficult to separate the truth from legends that have arisen around him.
One legend deals with the foundation of the Barony itself, and how in 3E 253, the Baron led an army of animals and men in a victory against the undead armies of Castle Wightmoor at the Battle of Wightmoor. Whether this is literally true or not, the people of the Barony celebrate a holiday called Othroktide on the 5th of Sun's Dawn each year as a memorial to the battle.
The Baron is even more famous as the man who stopped the invasion of the Camoran Usurper in 3E 267. Although the credit given to the Baron is probably overstated, it was at the Battle of Firewaves, not in Dwynnen itself but nearby, that the combined armies of Dwynnen, Ykalon, Phrygias, and Kambria defeated the Usurper and restored peace to Tamriel.