Heavily inspired by the mechanics of the same names in Europa Universalis IV; Events and Decisions is a mod and framework that hopes to inject a bit more historical flavor into the game, and to allow other mod creators to do the same. Events and Decisions is supported by the majority of modded civs and custom mechanics.
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Decisions are a set of choices a nation can make if certain conditions are met. Each decision has consequences, which can be both positive and negative. A nation never has to take a decision it is always at the players discretion whether to accept a decision or not. Some decisions are nation specific, some are religion specific and some are more generic.
The mod introduces an "Enact Decisions Panel" accessible through the Diplocorner drop-down. Decisions themselves are created/defined almost entirely via Lua (with XML/SQL for text and for certain effects via dummy buildings and policies), thus almost anything that can be done or detected via Lua, can be triggered or required by Decisions. The system is also modular, other mods can come in and introduce, remove or modify any existing decisions!
Currently, the mod does introduce a few other things into the game; many Decisions require Magistrates, a new resource, to be enacted. A number of Magistrates will be provided at the start of the game via the Palace, and more can be gained by constructing the Judicial Court, a new National Wonder.
As it stands, there are a number of Generic Decisions available to anyone, and 2 Religious Decisions that are designed to change depending on your civ's majority religion at the time (compatible with Tomatekh's mods). Each Firaxis civilization also has 2 Civ Specific Decisions, modded civilizations must have their Civ Specific Decisions supplied by their modder.
For a list of Civilization Specific Decisions, see here (Graciously completed by iBurst).
Events occur throughout the course of play. There are a whole range of events in the game, which can result in positive, negative and mixed outcomes for a player's country. They take the form of a pop-up notification on the player's screen, which may present a player with a choice, or may simply inform the player of the consequences and require they acknowledge the event has occurred.
There is also an Events system, also inspired by EU4 (and partly by Civ 4). With random events enabled an Event will occasionally occur. Events can also be scheduled to occur at a certain time; be triggered by other Events or Decisions.
My thanks to JFD for graciously providing events to incorporate into the base mod, to JanBoruta for his excellent artwork, to them both as well as Pouakai and Viregel for help with Decision and Event ideas; and to them all once again for help in playing testing the mod in it's earlier stages and providing feedback.