New units. Their discussion and selection of upgrades.

Well, if you lack knowledge and mana, I suggest developing advanced spellcasting – mana regeneration, fluctuating mana, and secret knowledge. Then you'll have enough for meteor showers and other spells. The only problem is that while you're worrying about ballistas and druids, if the enemy hero goes first, for example, Sinithar, and your ballista is already gone, what's the point? Besides, if you develop the hero in this way, it's no longer a Ranger, but a mage like Ashan, who combines combat machines with spells.