Yeah they are promoting a DLC sale while they're at it.
I didn't have this game, so very happy about it. How necessary is the DLC, is the base game fraught with issues?
The base game doesn't have a lot of issues, which is nice.
But let's have yet another DLC overview:
-Sword of Islam: Do you want to play as Muslims? If yes, get it. Otherwise, skip.
-Legacy of Rome: Adds some events and mechanics for the East Romans and Orthodox Christians, but, far more importantly, it adds Retinues (think small-scale professional armies) into the game. A must.
-Sunset Invasion: Aztecs invade at some point for unbalanced hilarity. Grab if you want, or don't.
-The Republic: Much like Sword of Islam, it only added mechanics (that the AI will use even if you don't buy it) for a new type of government: Merchant Republics. Much like SoI, grab it if you want them.
-The Old Gods: Makes all Pagans (and Zoroastrians) playable. Also adds a new start date in 867, makes revolts more complex and adds adventurer claimants. Pretty good all around.
-Sons of Abraham: Makes Jews playable, but the real draw is a bunch of mechanics and events for Christians and Muslims, and a scant few for Zoroastrians, including stuff like Muslim schools of thought and the Catholic College of Cardinals. Good stuff.
-Rajas of India: Lets you play as Hindus, Buddhists, Jain and Taoists. Just go up and read what I typed for SoI.
-Charlemagne: Adds a new start date in 769, viceroy mechanics, and the ability to make custom kingdoms and empires.
-Way of Life: Oh boy, this one is actually pretty damn important. Y'see, it adds these things called Foci. You pick one for your ruler and get a bunch of events and mechanics based on it. Doesn't seem like much, but it helps a lot in breathing some life in your medieval drama.
-Horse Lords: Play as nomads (if you don't have this, they'll be tribal instead), plus dynamic mercenaries, raiding adventurers and tributaries. The last one is pretty important for some mods.
-Conclave: Probably my favorite one. It revamps how the Council and liege-vassal relations work, as well as reworking both laws and the child education system. Also favors. Get it.
-The Reaper's Due: Adds a host of events while also revamping the disease system allowing for stuff like epidemics, medics, hospitals and closing the gates to your demense. Very, very good, but not critical.
-Monks and Mystics: Adds societies (some secret) that you can join and take part in, a fourth activity for each councilor to perform, the ability to set goals in wars for your allies instead of letting them run around on their own, mass executions/ransoming, and artifacts (there are a few in the base game, but most are here). It may seem like a lot, but it's one of the simplest DLCs around.
-Jade Dragon: This is a bit curious in one aspect: if you don't have Horse Lords, it also gives access to tributaries. Aside from that, it adds China as an off-map power that you can interact with, plus new Casus Belli.
Aside from that there's the Ruler Designer and Customization Pack, which are fun but very much optional. On the comstic side of things you have music, portraits, units and dynastic crests. Of these only the portraits will heavily impact your enjoyment of the game.