“Elia’s Quest” – “The Showdown” [Campaign 3, Mission 5]

Help me beat this mission. What’s the best way to defeat a garrison of 10k red-skinned militia? As soon as they approach, they wipe out everyone in 1-2 rounds. Ilia’s Meteor Shower takes out about 130 enemies per cast, while also hitting 4-6 stacks (depending on how they’re positioned) – about 500-800 militia are eliminated per round, and there’s only enough mana for 5 rounds. Also, my heroes don’t have light magic, so no resurrection spells :( However, I saw on this forum that it’s possible to defeat them with almost no losses (using Freya). How can I do that?