Demon attack.

I tried playing as the Light Elves on the "Hero" difficulty (version of the map DEMONS_ATTACK_V_1.1.1.). On the very first day, I captured the outpost protecting the sawmill (I managed to do this without losing any archer elves – the outpost was defended by 40 Miggers, so I had to sacrifice some fairies). On the second day, I captured the sawmill (it's basically impossible to do on the first day – the hero simply doesn't have enough movement points to reach it), but even with these resources, I couldn't build the "tree houses" to create forest elf archers by the end of the week – there wasn't enough wood – it simply wasn't available (three piles of 4 wood + 6 days of sawmill operation + 3 initial = 27, and to build, you need the 6th level of the city, i.e., 5 buildings, of which only the town hall doesn't require wood – that's 20 wood + 12 wood for building the archer generator itself = 32), and this determined the outcome of the subsequent events.
On the fifth day, Alaric arrived – by sacrificing two minor heroes, I managed to delay his approach to the castle until the beginning of the next week. By hiring everything possible, I managed to defeat him with my main hero (even though the danger was "high," and the Light Elves, unlike their dark counterparts, don't have any trump cards like "plague" or "hunters"). And then, as expected, a blue demon appeared – I defeated him, but almost all of my remaining archers were lost in the battle (the demon personally took them out), so when the yellow elf arrived, there was simply nothing left to fight with.

I think that this map, version 1.1.1, is not beatable for this race on "Hero" difficulty. I'm willing to acknowledge anyone who proves me wrong.