Okay, so from where I’m standing, Essence has never been in a situation where it can actually work very well.  The recent incarnation states that essence is used to convert an opposing philosophy’s land (Kingdom to Empire, Empire to Kingdom).  Now, the big fat problem with this proposition is that if it costs Kingdoms to change Empire land, it serves as a disincentive to attack the Empire.  After all, why burn the most valuable asset in the game when you can attack another Kingdom faction for free?

So my proposal is to reverse the phenomenon.  First, let me say that I’m not suggesting that essence shouldn’t still be immutable.  It’s not like mana or gold in which you can just keep producing more indefinitely. 

So without further preface, I propose that rather than have restored land cost essence… have it give you essence.  If you are a Kingdom faction, you would build irrigation systems or spend mana on restoration spells to bring forth fertility.  And what’s more, every Kingdom faction would gain essence from restored land wherever it happened to be in the world, not just the individual doing the restoration.  As a consequence, those Kingdom Sovereigns who have dedicated themselves to a lot of land restoration would gain positive diplomatic relations with other kingdom factions.  Those that don’t would be considered “free loaders” and be more succeptable to invasion from other Kingdoms.  So if you wanted to maintain peace with the other Kingdoms, a viable route would be to focus heavily on restoring life to the world.  Keep in mind, land restoration doesn’t have to be the only way in which Kingdoms gain essence.

Empires, on the other hand, could gain essence differently.  They might set up structures throughout the landscape--- hell nodes or something to that effect--- that transform the baren land to forsaken land and give a boost to their essence.  By this method, they do not share any essence with other Empires for restoring land, but on the same token, they gain no diplomatic bonuses with other empires on account of transformed land.  As a consequence, Empires would go to war with one another more frequently than kingdoms would.  In the end, Empires would have more raw power as individuals, but Kingdoms would be more likely to unite.  Kingdoms may even be able to enter into “Life-Binder” pacts in which each party is obligated to spend X mana each turn toward restoring land (at which point, you would also receive a hefty diplomacy bonus with said party.

Now, the role of essence would be different as well.  It could still be used to infuse champions with spell casting abilities, however a sovereign’s “free” essence would also represent the “casting skill” of the sovereign, a lot like it did in Master of Magic.  Major unit enchantments and most overland permanent enchantments would cost a certain amount of essence as well, which is freed up again once the enchantment is broken (while the enchantment is active, though, the sovereign has less casting skill because the essence is locked away.)  So our sovereign might have a lot of free essence and few enchantments or infused heroes, which would allow them to cast at a remarkable pace, or your sovereign might have a vast array of enchantments across his army and Kingdom but have a slow and arduous time casting new spells (because his essence is locked away in enchantments and heroes.)

Now, naturally, there would be other ways to gain essence, especially if you are a Kingdom.  It would be silly if all kingdoms always had the same amount of essence.  For instance, you might focus on an area in the magic tree that would enhance the essence you gain from transformed land.  You might even be able to give your sovereign a trait that improves by a tiny percentage of essence you gain from restored land each time your Kingdom transforms a given tile for the first time.  This would make land transformation more lucrative for some Kingdoms than others.  However, essence might also be locked away in dungeons or come from a one time infusion from a given tech. 

More interestingly, essence might also be captured from other sovereigns and champions who have it.  For instance, if you kill an enemy champion or sovereign with your champion or sovereign, you could possibly steal a certain percentage of their essence (the percentage improving if your hero or sovereign has special attributes.)

What happens to the rest of the essence that isn’t stolen or a sovereign/champion is killed by mundane soldiers?  It diffuses throughout the world.  How is it regained?  Possibly by something like a special essence focusers that are built atop a sovereign’s tower.  And there are some interesting things that could be done with this idea.  Some sovereigns might build these essence focusers on their tower with the explicit intention of sowing discord in the world so that they may funnel scattered essence toward their own greedy hands.  Scattered essence that isn't grabbed by focusers might even re-materialize in a neutral city, giving birth to a new sovereign and a new faction.  A devastating war may very well give rise to a powerful channeler on the other end of the world.  What’s more, you might give the Empires a natural propensity for capturing essence that has been “lost” to the landscape, infusing them with a drive to "destroy" while giving the kingdoms further incentive to avoid conflict with one another.

The possibilities are vast.