The game essentially ended on this save, but I don't see a point in continuing. In short:
The opponent took three 111s in a row and constantly re-stacked with some crazy units.
Then I tried to catch up and even re-stacked with mediocre units; eventually, I managed to do so. I had a total of 0 units across all 4 computer-controlled locations: two were desert, one was swamp, and the other was grassland. It took three days to reach the central grassland location from my castle. I struggled, had a powerful stack of 50+ Medusas, built Angels at the second location near the computer player, cleared the desert location, and reached the mountain range, which I had to bypass endlessly through the desert. Then I moved to the swamp, took three Hive units and one Utopian, but they didn't help much. Meanwhile, the opponent arrived through the central grassland location with full control, a dozen Griffins, and other powerful units. I immediately thought about evening the score. I fought almost perfectly (considering 15 mana for Shaktis, against powerful magic and 300+ mana for the opponent's units), essentially trading my stack of Vivs for the opponent's stack of Angels. I bought my way out and retreated to the underground location, which ran along the edge of the map, in search of better luck – and that's where the game was saved.
Given my recent result, I don't see a point in continuing to torture myself – I surrender. I haven't played such a frustrating game in a long time.

Thank you for the game!