CK2Plus (CK2+) is a mod originally created by Wiz, a member of the Something Awful forums who began working for Paradox in January 2013, which was then completely overhauled by a new team following the release of the Rajas of India DLC. The mod has had a lot of new features added since its original inception, and continues to be updated regularly. It also incorporates elements from other mods on the Paradox forums, as well as work done by other users on Something Awful's Paradox thread.
As the name implies, CK2+ exists to give you more—more content, more choices, more fun. The goal is to offer a deeper and more challenging CK2 experience without straying too far from the original game mechanics or adding overly deterministic events. The purpose of this mod is not historical accuracy (although we try to preserve it whenever it’s not detrimental to gameplay), but rather to enrich the medieval sandbox that CK2 offers.
Ultimately, CK2+ aims to deepen the CK2 experience, both in detail and enjoyment. Due to changes in mechanics that may make the game more difficult for new players, it's recommended to have first played the vanilla version of the game to have a good understanding of how it works.
Changes to CK2
- A completely overhauled factions system -- rather than solely having factions which go to war with their liege as soon as they are strong enough, there are also "common interest" factions which consist of vassals who meet regularly and can reward a liege who's kept them happy or make demands of a liege with whom they're angry...and who can start a civil war if their liege doesn't comply. These civil wars can be incredibly dangerous, as other factions can join in the war if the liege is unpopular. More information on how these factions work is available here.
- A cadet system for younger brothers of very large dynasties to establish their own dynasties if they should ever inherit a title. Likewise, powerful rulers who are part of very large dynasties but who not the head of that dynasty (and not closely related to him) may elect to start their own -- particularly if they are Muslim and part of a very decadent dynasty.
- A more logical system for adventurers -- adventurers will travel around to nearby kingdoms, attempting to raise money from sympathetic rulers and by campaigning in lands. Only if they raise sufficient funds will they be able to form a host, and the size of the host will depend on the amount of coin they raised as well as their individual prowess. A deceptive ruler may attempt to take their captive when they arrive and offer you them to you in exchange for a hefty ransom.
- A coronation system, which requires feudal kings and emperors to hold a coronation -- an event which invites not only vassals but nearby independent rulers and relatives -- which will solidify their rule. Until they are crowned, weak claims can be enforced against them and their Crown Authority can not be increased.
- A new tyranny system similar to EU:Rome. Kings cannot wantonly revoke titles, imprison, banish or execute subjects any more without incurring Tyranny. The "Tyrant" trait lowers relationships with everyone and in turn makes it more likely for vassals to revolt, and sufficiently high tyranny can cause a "dynastic stain" which is passed onto descendants.
- A unique map with many more provinces and territories, along with a revamped setup for de jure kingdoms and empires. One thing experienced players will immediately notice is the scarcity of de jure empires -- most empires are formed as titular titles first, and gain de jure territory through the course of the game.
- A revamped system of demesne laws. Crown Authority has also been changed, having the effects of the vanilla Centralization law folded into it, while simultaneously making it more difficult to raise (requiring a certain prestige score). Kingdoms and empires require a medium level of Crown Authority in order to enforce their de jure claims.
- Changing of Crusade/Jihad mechanics to more accurately and fairly represent large-scale holy wars. Winning a crusade/jihad results in the de jure kingdom of the war's target being created (e.g.: a successful Crusade for Jerusalem results in the Kingdom of Jerusalem being created and awarded to the victor), as well as the institution of a special truce to help Crusader states survive more than a few years.
- Adds a greater list of ambitions and plots, including: "Get a lover", "Break out of prison", "convert a province", "win a war", etc.
- A completely revamped set-up for the historical transition between Charlemagne and the Carolingian Empire to the Holy Roman Empire, with events allowing for this to occur even with the AI at the helm (or in a completely ahistoric manner). The de jure set-up for the Holy Roman Empire has also changed, with the former kingdom of Germany broken up into its individual "stem duchies" while under Holy Roman rule.
- The Mongol Empire, when it appears in the game, does so as a single empire -- and breaks up into the Ilkhanate and the Golden Horde (and possibly even the Chagatai Horde) if and when it's at a sufficient size and its ruler dies...just as the Mongol Empire did historically. This horde is a much greater threat than it exists as under vanilla mechanics.
- Expanded mechanics for female heirs and rulers. Women can now have their claims enforced by war even on agnatic titles, can have a martial trait which allows them to lead armies (though only in certain cultures, or at certain levels of gender law), and have special versions of some events (such as hunting and tournaments) which apply only to them.
- Changing succession laws requires prestige, and can cause anger not only among your vassals but particularly among those who find themselves disinherited as a result of the change. Some laws, like Feudal Elective or Tanistry, require the agreement of your vassals in order to change them at all.
- While tribal rulers cannot build new holdings normally, they will have pious characters sometimes ask to found a temple with their support. Their steward may also use the "Settle Tribe" ability in provinces of their culture to find a site for a new city -- which will require support and many years to build.
- The ability to disinherit an heir -- though an angry former heir may take arms against you, if he can find support.
- Expanded events for pagans, including new pagan religions such as Celtic and Ancient Egyptian -- many of which were adapted from the Ancient Religions mod.
- A "Shattered Realm" function, useable at the beginning of any game, which allows you to break up every kingdom or even duchy in the world and start everyone at the same level. It also has a function which allows you to change the world's starting religion set-up, making pagans dominant in many areas and all but removing Christianity entirely.
- Many new additional start dates, focusing on characters and periods throughout the era.
- A host of improvements for the AI, insofar as how they run their realms and how they use the existing events and wars a little more intelligently.
- A myriad of other new events and decisions, many of which are too minor to list here and also many of which are fixes for vanilla bugs or revisions of vanilla events & decisions to improve their function in the game.
One of the first things you'll notice playing this mod is that vassal limits have been greatly reduced compared to vanilla. It is considerably more difficult to manage a large empire, and you will have to decide between having many vassals or having a large personal demesne when considering whether or not to increase your Crown Authority. Retinues are smaller and more expensive to maintain, and the benefits of some technologies has been spread out so there's unlikely to be any single technology which stands above all others in its usefulness.
Another major thing you'll notice are the factions. There are still factions vying for independence and to support a claimant against your title, and you'll have to watch out for them, but there also factions with names like "Prosperity", "Glory", "Tradition", and "Court". These are the common interest factions, and each one determines what the vassals within it want -- do they want peace and wealth? Do they want a strong ruler with lots of prestige? Do they want a pious ruler who doesn't change from the old ways? Their faction determines what they do or don't like about what you do, and when they get unhappy as a group they can suddenly start making demands of you. A civil war can be incredibly bad news if multiple factions are unhappy and all your vassals band together against you instead of letting you pick them off one by one.
In general, quite a few of the changes lead to gameplay being more restrictive on your personal power especially regarding acquiring new lands which, depending on your personal playstyle, can either be a bad thing or lead to a deeper, more involved vassal-reliant game.