Advisors

ESU features 24 unique advisors, many of which are flavored variations of the 21 vanilla advisors, as well as a unique government reform available called "Court of Darkness" at tier 31 which allows for an additional 12 dastardly advisors to help or haunt a player's court. Depending on the starting culture there is a diverse panoply of advisor portraits which represent the races of Tamriel for their respective nations. Advisors in Elder Scrolls Universalis may still be upgraded with the requisite DLC however they may not be promoted past skill level 3.

Court of Darkness
At government reform tier 31 there is an option to select the Court of Darkness reform, which allows  -50%  advisor costs and unlocks 12 unique advisors which provide a large positive effect and a skill scaled negative effect.

Court of Darkness is not available if any of the following government reforms are enabled:
 * Oligarchy
 * Human Republic (Dutch Republic mechanics)
 * Monastic Elections
 * Reason and Logic
 * Bureaucratic Tyranny
 * Divine Right
 * Subservient Bureaucracy
 * Justified Atrocity

Light vs Dark Mechanics
Additionally, if the player has Res Republica DLC enabled, this reform provides a Light Advisors vs Dark Advisors Mechanic (the same mechanic is enabled for most of the government reforms which prevent this one),

Where dominance of the dark side offers: While dominance of the light side offers:
 *  -25%  Culture Conversion Cost
 *  -50%  Leader Cost
 * -1 Legitimacy per year
 * +25% Core Creation Cost
 *  +0.5  Diplomatic Reputation
 *  +1  Legitimacy per year.

Legitimacy
Each of the base 24 advisors have a second scaled modifier by skill level, and scaled legitimacy modifier of -0.15 a year per level. So a level one advisor would give -0.15 legitimacy equivalent a year, a level 3 advisor -0.45 legitimacy a year and 3 level 3 advisors -1.35 legitimacy equivalent a year. These mechanics are reversed for meritocracy, such that if playing as Emperor of Akavir each advisor grants  +0.25  meritocracy per skill level per year.

Religions
The following religions offer various mechanics related to advisors:
 * Cult of the Old Gods: -25% Advisor Cost
 * Reclamations Pantheon:  -25% Same Culture Advisor Cost
 * Sload Faith: +1 Possible Advisors

Advisor Portraits
The advisor portraits used as examples are representatives of the Imperial Culture. Additionally, ESU features 24 unique advisors (12 male and 12 female) for the following cultures:
 * Nords
 * Bretons
 * Redguards
 * Imperials
 * Altmer (High Elves)
 * Bosmer (Wood Elves)
 * Dunmer (Dark Elves)
 * Dwemer (Dwarven Elves)
 * Snow Elvers
 * Maormer (Sea Elves)
 * Khajiit
 * Argonians
 * Kothringi
 * Lilmothiit
 * Orcs
 * Imgans
 * Minotaurs
 * Sloadians
 * Vampires
 * Akaviri
 * Tsaesci
 * Tang Moans
 * Po Tunians
 * Dremora
 * Kamalians

Missions
There are two missions within the administrative line, in positions 5 and 10, Obtain Prestige I and II, which require 25 and 50 prestige, respectively. Completing Obtain Prestige I grants one  additional advisor and completing Obtain Prestige II grants  -10%  Administrative Advisor Cost. These effects last until end of game.

Classical Age
In the first Age, the Classical Age, between year 0 and year 190, one of the requirements is have a Natural Scientist Advisor. Additionally, an ability that can be purchased is Classical Great People, which offers  -15%  Advisor Cost.