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If you have a strong hero, you can defeat even 100 Phoenixes and 9999 Long Dragons, but you need to ensure that you go first or have the Cursed Armor and Vulnerability Medal; then they will be defeated easily.
The maximum amount of mana is 3960 (I calculated it in my head, so if I made a mistake, please don't be too harsh). This is enough for a long time.
Wow! I was writing the letter after the test, and here's what I came up with: 100 Phoenixes divided into 7 groups against Lazarus, also divided into 7 groups, and then into 5, 4, 7, and 3, and 1 (4000 in total). Several tests.
The hero has maximum defense, attack, magic power, and knowledge. Secondary skills: All schools of magic, expert wisdom, intelligence, magic, defense, attack, and leadership (Sir Mullich).
And in all battles, even if not on the first try, I won! Thanks to Berserk and summoning elementals! The artifacts were: Cursed Armor, all spheres of magic, Vulnerability Medal, and Badge of Courage.
I placed a Conflux with the Grail and a Dungeon with the Whirlpool.