Dark Essence/Darkening Units
With the daily weakening of Eir and the slow death of our sun, only the Beacons stand between us and the coming night. Balur and his Marennon masters know this all too well, and even now they drive their Black Horse to occupy them. This must not come to pass or all shall be lost. Any League that captures a Beacon must defend it from increasingly powerful waves of the Black Horde (and the armies of rival Leagues). The battles will be brutal, but you will have one secret weapon...
The strong enchantments woven into the foundations each Beacon have the power to trap and store the Dark Essence of all of Balur's spawn slain during the defense of your League's Beacons. Your League may use this Essence to perform a forbidden ritual to "Darken" your own units - imbuing them with a spark of the evil that grants Balur's forces their strength. This will reduce their need for food, increase their defensive and offensive statistics, and improve their effectiveness in combat. All Dark Essence reclaimed from fallen Black Horde units is stored within the Beacon where the battle took places, and can be accessed by any Member of the League what had units participating in its defense.
Darken different Unit types by upgrading a Beacon's level:
Level 2 - Infantry
Level 3 - Cavalry
Level 4 - Occult Units
Level 5 - Bestiary Units.
Bear in mind that a Beacon will attract more Black Horde creatures with each additional upgrade level. This in turn will provide you with more Dark Essence, with which you may create more Dark Units.
Transferring Dark Essence
The League Marshal and League Captains can ration Dark Esssence to different Beacons as they deem fit, although some Dark Essence will be lost depending on the Beacons respective levels and distance from each other.
Performing the "Darkening" Ritual
Send Units to one of your League's Beacons and open the "Darkening" window. Select the number and type of Units you wish to Darken, and press 'Darken'. You can review the history of Darkening Rituals performed at the Beacon from the 'Darkening History' window in the Beacon interface.