Unity of the Elements

Where can I get so much experience to obtain the "Arcane Sight" skill? It requires at least 25 levels.

There's plenty of experience in the library; just keep collecting it. The Academy's scholars also contribute to gaining experience through their education. The "Luck" skill is beneficial, especially if acquired early on. Additionally, I found and equipped the "Enlightenment Amulet." Plus, visiting the library with a Sphinx (Heroist is right, it provides a significant experience boost) results in the hero reaching approximately level 28.

to Heroist. In my opinion, the fact that the hero gains a huge amount of experience almost effortlessly at the start of the map doesn't improve the gameplay. It would be better to spread out the experience gain: reduce the amount from the Sphinx, reduce the amount in the library, and slightly decrease the enemy strength.