Warhammer-Empire.com

I watched it too. Good to see Empire getting some eyes on it.
On lists, im still in testing, but less shooting and infantry than Mordian took with more Cav and DG's with very smart play could work v. Well

My understanding of Fear and Terror is that they work as they always have. That a creature that causes Fear only suffers Fear from a creature that causes Terror.

However, it has been pointed out in another venue that there is nothing in the rules that explicitly makes units that cause Fear immune to Terror.

How about the part in the rules that say that models with Fear instead Fear models that cause Terror? Seems clear enough for my gaminggroup at least.

They arent immune to Terror but they treat it as Fear, so theres no need to explicitly say that they are inmune terror because it would be irrelevant.

Honestly, given how incredibly shit of a rule Fear is in general, its  interraction with Terror is the best part of having it.

I understand your point of view but I am trying to understand why is so, because I cannot find anything RAW that clearly points in that direction.

According to my reading, in the section MODEL PROFILES, it is pretty clear that the models are the ones that get the rules (subsection "Special rules") and when they join together the unit applies the rules from the models (so the "unit" itself does not have any special rule). This is implied in the section "Unit size" and in the way is written Characters & Formations.

On the other hand, reviewing how is written "Master of Battle" special rule implies that units and character are different entities and units can also get rules. Or it is just a shortcut for "all other models in the unit".

Master of Battle: If this model joins a unit of Empire Knights, Inner Circle Knights or Demigryph Knights, that unit will gain the Immune to Psychology special rule. Should this model leave a unit it has joined for any reason, that unit loses this special rule.

So, IMHO  when we are adding more models to a unit, they add their rules to the unit (when we are creating the army list, they are actually copies of the same special rules except for characters). That's why we also get some special rules written "all models in the unit" or "majority of models in the unit".

IMHO and I guess RAW a unit has a rule when any of the models has the rule. Therefore, a model with Frenzy, Hatred (X), Immune to Psychology or Stubborn joining a regimental unit with dettachments should confer those special rules onto its detachments whilst they are within 3" of it

Also RAW, although the Witch Hunter's Immune to Psychology is not extended to the other regimental unit's models, when we check the "majority of the models" condition is not fullfilled and the unit ignores "automatically passes any Fear, Panic or Terror tests" and also can flee as a charge reaction. However the unit still has the special rule.

So, in one scenario, if a character is a separate entity when joins a unit (as implied by Master of Battle), then we can only provide the magic items (and the sweet additional special rules) to a champion or standard bearer to add the rules to the Regimental Units and then extend it to the dettachments using the Dettachment special rules.

In the other scenario, if a character becomes part of the unit when joins it, his special rules are added to the unit special rules (although they may not be applicable because of the "majority of the models" restrictions).

I also checked the FAQ (https://www.warhammer-community.com/wp-content/uploads/2024/01/ScGm8K4WG9pa9sGv.pdf ) and the change to the weapon only says:
Page 339 – Berserker Blade
Add the following note to the weapon profile:
‘Notes: The wielder of the Berserker Blade is Frenzied.
So it still gets the Frenzy rule.

I think it was specifically addressed in the FAQ re the bezerker blade to clarify that the unit does not get frenzy, only the model with the blade

You can take priest of Ulric with gw knights. The reroll 6 for enemy prayer adds a little to their survivability which the Demi's can't get.

True, but if your opponent hits you on 4+ that prayer is just the same as having -0,5 to hit on them (even worse if they hit on 3+) + it only works 58% of the time + the priest costs more than than an extra DGK would.

I get trying to get subpar units to work, but we truly have become masters of polishing turds on this forum. 
A direct consequence of our army being filled with them I suppose...