What is the path of blood for?

[Question]

But you can only build a single mage a turn per fort(and you cant even queue them), which is a pretty huge limiting factor (not to mention collecting them from all the forts), and they are so squishy they die to cavalry/flyers in melee. And you probably need to give them boosters to cast decent battlefield spells too.

Im surprised by how deadly frost fiends are though. With only protection 9, i expected them to die a lot...but im fighting Formoria with the "stop AI from building chaff independant troops" mod, and facing mostly Formoria giants...and im taking almost no casaulties at all despites being outnumbered 4-1 and not even using any buffs or battle magic at all. How is that possible?