"Mirror armour" is a type of partial plate armour which was developed initially from round metal mirrors (or any other type of metal capable of bouncing light) worn over other armour (usually over mail) as reinforcement. Metal mirrors in this armour were considered as protection from not only cold steel and arrows, but also supernatural influence as it was believed that mirrors could reflect the evil eye, so they were polished and worn over other armour. The mirror in Tzarina Katarin's tent suddenly cracks because the Daemons of Chaos are too powerful to be repelled by it.
Kislevite Winged Lancers and Gryphon Legion cause fear. This is exactly what plumages used by real-life Winged hussars were made for. They caused a pretty intimidating noise on the charge that scared enemy horses and infantry.
Of course Kislev can revive Ursun in their endings; they've spent their entire campaign gathering Devotion, after all, and Warhammer gods (at least partially) subsist on the worship of their people.
Even though they are extremely dangerous locations in-game, some still take issue with the idea that mortals can traverse the Realm of Chaos and escape with great prizes. However, while the game was initially implied to have a theme of the ultimate battle between Order and Chaos, the actual plot of the game is closer to Be'lakor vs Everyone Else. In other words, while the Chaos Gods would obviously prefer to take advantage of the situation themselves, they have every reason to turn a blind eye to a few mortals if it means that Be'lakor doesn't benefit.
Besides Khorne apparently finding it amusing to leave Skarbrand exiled for all eternity, there's actually a very good in-character reason for him not to take the latter back at the end of his respective campaign; Khorne is a god of warriors, not grave-robbers. He doesn't want skulls for their own sake, he wants skulls indicating that battle and carnage have taken place. Skarbrand, however, neither fights nor kills Ursun - he wasn't even there to watch him die. While Ursun's skull may be very large and impressive, it's probably not considered a sacrifice worthy of Khorne in the first place because of the manner it is acquired.
There's also a few other factors as to why Khorne would keep Skarbrand exiled.
One is that Skarbrand made a deal with a mage to get to Ursun. Khorne hates magic and views it as cowardly; the very few exceptions to this rule (e.g. a Khorne worshipper being a Magic Knight) are those who use magic to improve their melee in some way. Skarbrand fulfills none of the exceptions, relying on magic to chase this goal.
Another is that the Advisor's own price is a drop of blood. One of Khorne's key tenets is "Blood for the Blood God", so allowing even a drop go to anyone else is considered heresy.
Finally, it's been said that Khorne actually likes Skarbrand better this way. The reason he was initially exiled and given insatiable bloodlust was because Skarbrand tried to backstab Khorne and take his place, his pride fuelled by a ploy from Tzeentch. For this reason, Khorne squeezed all personality and desire from Skarbrand and left behind only his bloodlust, making him more loyal to Khorne's cause than ever before. Undoing that would open back up the possibility of Skarbrand betraying him again and not serving as well as before.
The ending's reveal of this game as a Stealth Prequel retroactively explains a lot.
Why is Kislev such a nonentity in the first two games (aside from the obvious out of universe reasons)? Easy - they'd expended so much of their forces invading the Chaos Wastes themselves. It is a glorious victory, but doubtlessly it cost them. The multi-year winter in Ursun's absence also severely mauled their primitive economy.
Archaon's invasion of the Old World in the first game is pretty anemic and Order almost always crushes it with ease. His army also seems to consist almost entirely of Norscans and Beastmen. Where are the Kurgan and Daemons who flocked to his banner by the hundreds of thousands in both the Storm of Chaos and End Times timelines? Well, in Total War, the daemonic offensive against the Old World already happened in this game before Archaon was crowned - and got crushed, badly. The Kurgan meanwhile suffered severe losses against the Cathayans, Kislevites, and Imperials, so no surprise they don't have much to contribute to Archaon's army just a few short years later.
Regardless of whether they won the campaign, Cathay is likely trending upwards after it - which would further distract the attention of the Kurgan and Daemons, especially since the Cathayans are now willing to go on the offensive.
The implication that Tzeentch masterminded this game's events actually gets well with it leaving Chaos weakened enough for Order to easily avert the End Times. Tzeentch hates his fellow Chaos Gods, and as the god of change and scheming would be the least enthusiastic about just blowing up the planet. Even if he wanted to, he's known for screwing himself over constantly just to keep himself existing through paradoxes. Also, Canon Foreigner Sarthorael being Tzeentch's right hand daemon in the first game instead of Kairos is probably because the Kislevites or Cathayans slew Kairos in this game, and it takes centuries for a daemon to regenerate in the Realm of Chaos.
One of the final Bretonnian quest battles, where the knights crusade to the Chaos Wastes to finish off Archaon, may very well have been inspired by the Kislevites and Cathayans showing them it was possible in this game.
Greasus is Abled in the Adaptation because he has yet to gain the excess weight that will eventually leave him immobile.
Though it's not made entirely clear when the Vortex-campaign sits in the timeline, the events of the campaign explain the absence of actual Daemons. The Vortex being as warped and weakened as its described should've conceivably allowed the Daemons to come through en-masse, but after suffering such a serious setback, the Chaos realms may not have had the strength to breach the Vortex. In turn, the Chaos Gods absence could've allowed the Horned Rat (who, compared to them, is little more than an arrogant upstart) to elbow his way into the spotlight.
In the Immortal Empires trailer Thorgrim dismisses Teclis's speech as 'just another Elgi scheme' and asks if Teclis really speaks for his people. While it makes Thorgrim look like a petty Jerkass considering the circumstances, those who know Teclis's backstory or remember the High Elves' campaign from the second game will see it for the Armor-Piercing Question it really is - Teclis is notorious for going rogue and not working with his fellow High Elves. He doesn't speak for his people and Thorgrim knows it. Thorgrim is angry at being called short, certainly, but Teclis also tried to dodge the question, which he (in Thorgrim's eyes) would have no reason to do if he were acting in good faith.
