The 8th stage of the John Van Caneghem Tournament (Interportal).

112... that early? And with what army?
It's clear that you need snipers, dragonflies, and mass slowing, but...

Well, you wrote it all yourself :) All that's left is to implement it. What's the problem???
On the first day, capture all cities except Necropolis. Place a fast hero in front of the Efreet, focusing on speed. Someone takes Pandora with experience and the Book of Earth, leveling up Expert Earth Magic and Archery! (other useful bonuses are welcome. Ideally, at least get basic Tactics). And this hero gets the Dragon Crown.
On the second day, gather all archers and upgrade them to Snipers with the help of Jelu (get to 20+), add dragonflies, orcs, and lizards. Learn Blessing from Adela and go. You need to position them correctly and shoot effectively.
After the battle, the logistics hero captures Necropolis and kills Galtran.

Efreet or Ifrit?
In the physical copy, one thing is used, and in the game (complete collection, Book Edition), another.

This is a philosophical question. Personally, I think that Efrit is correct, as in the original, but I don't know exactly how it's translated into Russian, but it seems to be E.

I think that the Book of Earth + a leveled-up mage on level 112 can defeat Ifrits.
The idea is to place many Earth Elementals, but I haven't tested it.

Unfortunately, there is cursed earth, so our spells only work for Slow and Bless.