Auto-translated
With 60 Thunderbirds, 16 Mummies, and 14 Manticores, you won't kill the last Blue hero who has 150 or 180 Archangels and a whole bunch of other Heaven units; no Dark Magic will save you there, because your Thunderbirds will immediately die from the Archangels, and the rest won't even have time to attack. That hero has an attack of 40-50...
Added 1 minute ago
There's no point in running after Sandro's Cloak when you can go directly to Chaos.
Firstly: I killed this hero without losing any of my units. Dark Magic helped A LOT, + COUNTERSPELL. (Luckily, there's a save, I checked, that hero has an attack of 26).
Secondly: The question is, can you complete the game without killing the Blue hero?
If YES, then I will accept your post as a statement. If NO, then why so much distrust? (In my opinion, it's not good to immediately call someone a liar).
P.S.: I was a little off: 62 - Thunderbirds, 7 - Manticores, 16 - Mummies. (Plus, I want to add that there are 3 Blue players in the game, I described the strongest one in my opinion above, maybe the attack of 40-50 was for another one, in any case, I didn't take more than 62 Titans into the army, because I was afraid of not completing the Sulfur quest.