You're like a real wizard, Zveroboy! The map is quite challenging, but I read your posts, and I still don't understand how to get so much mana from the Leprechauns. When Sandro is killed, I can't take the tomb because the Imp is being attacked, and the spacebar doesn't work:(

The technique for pumping Sandro's mana with Leprechauns for OptiMAL.:)
(The battle takes place right at the Fortress gates; the idea was actually suggested by the players
Undergrounder isn't participating in the tournament due to a lack of free time, and neither is IronAxe)

First, you need to move one skeleton from the Fortress to Sandro, then move this skeleton away from Sandro, behind the Fortress. Then, with this skeleton, you can collect the Ore that lies at the Fortress gates. Next, open the Fortress menu and drag Sandro into the garrison.
Then, with the skeleton that collected the ore, stand on the spot where the Ore was lying.
After that, go back into the Fortress menu and drag Sandro and two Imps from the Garrison to the skeleton. After all these procedures, Sandro should take one step and return
to his old position; then, the Leprechauns will attack him on their own. During the battle, you need to
wait until the Imps drain all the mana from the four Leprechaun units (that's 12 units). Then, let the Leprechauns severely beat Sandro, and the battle will end, and you'll see that a tomb lies near the Fortress. Now, just enter the Fortress; Sandro will immediately revive and have full health and 52 mana instead of 40, and only one turn will be spent. If you think that's not enough mana, repeat the process again. I managed to pump up to 166 mana this way.

But, to be honest, I didn't use this ability in the walkthrough.:)