Impossible, Mage - No unit loss.

[Quelthos]

I am on a similar quest - impossible, mage, no unit loss - up to level 16.

My current strategy is little more than starting every combat with double level 3 geyser spells. Distortion is my clear cut favorite for keeping control of a fight - I only recently acquired Geyser and Phantom, and mostly relied on slow/trap up through the forests and pirate islands.

I leveled with archmages, archers (priests vs. undead), royal snakes, inquisitors, and horsemen. Took on evil beholders and royal thorns when I found them in the pirate islands. My current army is cyclops, giants, royal snakes (+frog Feonora), inquisitors, and evil beholders.

I've had some luck with spells - gift in the islands, resurrection in a hidden chest in dwarven mines, and geyser after completing titan's tear quest. Hard to imagine where I'd be without those.