Marthar is a Breton Arch-Mage from Daggerfall. He is also a massive pervert and often uses a unique Transfiguration spell to shapeshift to 'peek' on women.
Marthar was captured by the Imperials, under the impression that he was a Stormcloak Soldier, when he was exploring Skyrim. Marthar is also the current Arch-Mage of the College of Winterhold. He probably wasn't attending the College at the same time as Phantom-Fish.
Marthar often has nude parties with Alice and Alianor in the Honningbrew Meadery. He will often say things like "Victory! Or Sovengarde!". This is unusual because he is a Breton. He even sounds like a Nord.
- The reason Marthar often speaks with the Nord voice is because VFTD never fixed his voice. He thought it was a funny addition to the series.