Arcana

Arcana is a gameplay mechanic specific to the Ardent Mages faction which provides a number of abilities in the form of Pillars and Spells at the cost of Dust.

The power and cost of these abilities increases with their Arcana level; both Pillars and Spells start at an Arcana level of 1, which can be increased up to 5 from technologies that are either researched or obtained as quest rewards. The following technologies increase Arcana level:
 * Dust Purifier: +1 Arcana level for all Spells on Empire. Can be researched in Era II.
 * Dust Mechanics: +1 Arcana level for all Pillars on Empire. Can be researched in Era III.
 * Painosphere: +1 Arcana level for all Spells on Empire. Can be researched in Era IV.
 * Sacrificial Amplifiers: +1 Arcana level for all Pillars on Empire. Can be researched in Era V.
 * Secrets of the Virtuals: +2 Arcana level for all Pillars and Spells on Empire. Obtained as a reward for completing Chapter 8 of the Ardent Mages faction quest.

Pillars
Pillars are temporary structures that provide bonuses in an area around where they are placed for 10 turns. All Pillars start with a range of 1, affecting the tile they are placed on and the 6 adjacent, but this can be upgraded as the Arcana level of pillars is increased. While they may be placed outside regions you own, they cannot be placed on: Additionally, active Pillars will block the ability to build Districts where they have been placed, so it is important to plan Pillar placement around City expansion.
 * Districts (including districts under construction)
 * Villages
 * Ruins
 * Sea or Lake tiles
 * Ridges
 * Wasteland
 * Any tile where you do not have vision

There are a total of five types of pillars, each providing a different bonus and obtained from a different technology. Be aware that the actual effect of each Pillar depends on its Arcana level, and can be found in full detail on their pages.

The cost to place a pillar depends on the Arcana level of the Pillars as well as the total number of Pillars already in place. With "N" being the number of pillars already placed and "A" being the Arcana level of pillars, the cost to place a pillar is:

Cost = 20A(N+1) + 5A2 + 15(N+1)2

To simplify this somewhat, here is a table containing the cost equation for each level of Arcana, where "N" is the number of pillars already placed:

Spells
Spells - also called Incantations - are immediate effects that can be used in battle to provide buffs or debuffs in an area for up to two rounds. Upon using any spell there is a cooldown of two rounds before you may use another one.

Unlike Pillars, which have restrictions to where they can be used, spells can be placed anywhere, including on tiles outside the battlefield you have no vision on; however, it should be noted that placing a spell outside the battlefield will still be counted as using it, costing Dust and enacting the spell cooldown. Additionally, while it is possible to place a spell from one active battlefield onto a different one, the spell will not affect units that are not part of the battle it originated from.

There are a total of five spells, each providing a different effect and obtained from a different technology. Be aware that the actual effect of each spell depends on its Arcana level, and can be found in full detail on their pages.