I can't complete the game if I side with Hade.

If I refuse his offer, once I enter the mage guild, I see this and everything works fine:

while, if I accept, the same window flashes for a short instant and then disappears:

(there's a trick though: the "Continue" button is in the same position of the button I clicked to enter the building. So I double clicked very fast and I was able to start the fight against the guild leader and finish the game)

Edit: in both cases I saved Ayda, if it matters