Pfft, I had a character at level 78; I played a lot and grinded back then.

Actually, the maximum level is 70. I checked using a code to increase the level (by the way, after level 68, you can't increase the level further using a code). After reaching level 70 (I got the last two levels using ancient wisdom), I visited the dragon coliseum, and another tree of wisdom – an inscription appeared with approximately the following content: "The hero has reached the highest level of experience." Perhaps this is possible in a pirated or original version of the game (I checked on Whirlwinds). But when hovering over the experience in the hero's parameters, a message appeared indicating a lack of experience for the next level: "-8389 experience units" or "-8389M experience units." So, through experimentation (although this maximum was known even before), the limit of development for a hero has been determined.