izigame.me

tl;dr: Wait for a 75% sale.
As with all DLC releases, the 1.12 patch also came with a free patch. This patch was accompanied with (among other things) the introduction of a new legitimacy mechanic, which gives you maluses if its value is too low and positive buffs if you increase it past a certain threshold.
This paid DLC adds / unlocks:

Ways to specifically increase your legitimacy via three already existing activities ("Espouse Legitimacy" intent unlocked via a tier three dynasty legacy -> feasts, grand tours, grand weddings). This feels kind of backhanded, since legitimacy itself was part of the free update.
Funerals: An activity which makes you lose like 600 stress and takes months upon months to complete? You may also use the "Espouse Legitimacy" here to increase your legitimacy immediately after your previous ruler has died.
The Black Death – I’ve got to be honest, I’ve actually never experienced it in any of my games, because I’ve left it at the historical game rule setting and all of my games end way before reaching that year.
Two more dynasty legacies. One further boosts the legends mechanic; the other one is tied to legitimacy, making it easier to amass the latter. The former subjectively did not feel impactful at all.
Legends, the namesake addition of this DLC. Mechanically, it works similar to diseases on the actual game map, just in reverse: Legends spread within the baronies of (mostly) your own realm, providing steep bonuses to each of those provinces. They come in three tiers and may be “completed” during any of those tiers. Completing a legend stops its spread on the map and may provide you with a special building slot or a new one-time mechanic such as a migration casus belli or the ability to diverge your current culture into one of an ancient heritage, such as Hunnic, Hellenic or Gothic, though those new cultures don’t provide any new mechanics and may otherwise be accessed via the ruler designer prior to starting the game, even if you don’t own Legends of the Dead.
They are a much needed late game gold sink, but they are sadly entirely detached from the rest of the game. Unless you intentionally enter their specific menu and manually start a legend, you will never feel their impact in your game. Nothing ever triggers anything relating to legends organically, unless I am forgetting something.
To make it worse, their related event pool seems to consist of the same ten meaningless events which are thrown at your face over and over and over again. Would you like to increase the per barony spread chance of 0,25% by a multiplicative increase of 2% or decrease its upgrade cost by 50 gold? Would you like to convince this baron to spread your legend even though they can’t even realistically each and thus actually spread your legend on the map?
This issue is compounded by the fact that the rest of the game does not acknowledge past legends. You are only reminded of past legends if you specifically enter their designated map mode and notice the colored baronies. There are no mentions of it anywhere else.
Legends are initialized by using a legend seed. There are generic seeds which you can access by for example holding a holy site of your faith. Some legend seeds are given to you via decisions, mostly those who create a new de jure title on the map. At game start, there are several unique legend seeds which may only be used once to access some of the aforementioned one-time features (e.g. a migration casus belli, ancient cultures). This is not limited to players only, meaning you are effectively encouraged to quick start your economy to claim a special legend seed before some random AI character picks the legend seed before you click its button.
Legend inheritance is currently a frustrating mess: Once the holder of a legend dies, their dynasty members may claim said legend instantly for free until they themselves die. If you happen to forget to instantly pause the game and take over your current legend with your new ruler, some insignificant member of your dynasty is likely to take over your legend, realize they can’t possibly afford its maintenance and end it immediately – which is utterly frustrating if you lose access to an unique once per game legend seed this way.
Two of your courtiers, your chronicler and musician, may also provide negligible bonuses to you while you are spreading a legend.

Verdict:
I received this DLC as part of the chapter three DLC bundle. I know it’s on me, but I never actually checked the supposed “tier” of this expansion as it would be unlocked for me anyway. After playing with it for a while, I considered this DLC to be a small cute 5 € addition to the game similar to Friends and Foes. Unless you go out of your way, you will never feel this DLC’s impact in any of your games. And if you do, it’s only in the way of numbers and modifiers, similar to a court artifact which cost obscene amounts of gold that you can also not repair.
It’s something small you can click later into the game if you plan to upgrade the legend to its final tier due to their high maintenance costs, but it doesn’t otherwise interact with the game nor change the way you play the game in any capacity.
Well that was until I actually clicked on CK3’s store page weeks after playing with this DLC. Apparently it’s full price is 20 €, not at all within the 5 € price range I had expected after playing around with it for a while. In hindsight, if I had not purchased the chapter three bundle, I would have at most paid 10 € for this. But as it stands, I feel disappointed with this DLC as it sadly takes up an entire “big” DLC slot of this DLC pass.