The Quest for Truth

Markel is one of Sandro's favorite students, but the exact time he joined the Voidwalkers remains unknown. Nevertheless, at the time of Sandro's death, Godric, Cyrus, and the others were still young, while Markel must have already spent a considerable amount of time under the tutelage of his mentor. Consequently, he lived a very long life and certainly witnessed the eighth century, and perhaps even a significant part of it. Otherwise, Markel studied with Sandro for only five years, and it's unclear how he became so intelligent.

The eighth century, Astral, is 701-800 AD. That means Markel must have been around 250 years old at the time of the events in the fifth Heroes game. Some mages of the Seven Cities could live to be 200 years old, but they were already frail old men. Markel is not young, but he is definitely not a frail old man. In Clash of Heroes, as a reminder, the events take place about 30-40 years before the events of the fifth Heroes game. And Markel is there, and he is quite young. Yes, older than Godric, Aidan, and the others. I would assume he is about 35 years old there.