“Flight to Salvation” – “Deeds and Paths of Darkness” [4th campaign, 1st mission]

I went back to playing through the campaigns and discovered a tactical trick in this mission that I initially overlooked: under no circumstances should you surrender the Academy town. If Zephyr is defeated on the map (by the same elves in an unequal battle), he will be transported to the tavern in that town, where you can safely buy him back!
The only downside is that all artifacts are lost (or fall into the enemy's hands?).