The spell's effects in the RPG are obviously open to GM interpretation, and I know that some GMs probably wouldn't allow such a thing because it "betrays the spirit" of the spell, but Boney has always been flexible with his interpretations.
It's also partially because there actually is gives me a way to let Celestials actually do divination without having to come up with fluff for the Portent of Amul spells, which in the RPG directly affect the actual dicerolls with barely a handwave in the direction of what it looks like from an IC perspective.
I'll be honest, I instantly thought of Mathilde when Goendel mentioned the long shadow, so I thought Mathilde was referring to her past self when she was talking about more ambition than skill until the whole Vampire thing. I think this misunderstanding was funny. Either Mathilde was overthinking things or she was being humble, because I've found that while Mathilde enjoys headpats and recognition (look no further than her complex on naming things after herself), she isn't very comfortable recognising her acheivements in Stirland. The bad memories are probably a huge part of that, but it's also possible self criticism over her past self and imposter syndrome. Old Mathilde was not good enough to save Van Hal, so she can't accept being praised for her accomplishments.
That's definitely part of it, but another part is that Mathilde generally doesn't think of herself as having an affect on the world, she thinks of what she does as undoing or preventing the negative affects of others. Part of that is the influence of the Grey Order, who are generally a reactive force that remove negative influences instead of a proactive positive influence, and part of that is the influence of living among the Dwarves, who are all about restoring things to a glorious past instead of building anew a better future.
To mangle a quote: A good Grey Wizard knows their whole job is to make someone else look good, keep someone else safe, help someone else do what they were put here to do. A good Grey Wizard stays out of the spotlight. If they're doing their job right, you don't even know they're there. Once in a while they might step on stage just to fix a problem, to set something right. But then before you even realize they were there or what they did, they're gone.
My first reaction towards this was that "she must be exaggerating right?". Being the pedant that I am, I checked and noted that Ghouls have a Toughness of 4, just as high as an Orc or Dwarf (and 1 point higher than humans and Elves). They are not necessarily as fast as Skaven, having a movement of 4 and an initative of 3 vs Skaven's movement of 5 and Initiative of 4 (Clanrats. Stormvermin are Initiative 5). Skaven give Elves a run for their money.
Lower movement and initiative, but more base attacks. And though they have the same base movement as a zombie in the tabletop, in most lore depictions and in Total Warhammer they're significantly faster than them. Tarni could be exaggerating, but not by much.
There are also Crypt Horrors, giant mutated brutes that are basically Ghouls that consumed a Strigoi Ghoul King's blood, just like Terrorgheists are Fell Bats that consumed a Strigoi Ghoul King's blood.
Crypt Horrors is what they mean by 'ghoul vampire'. Vampires might avoid acknowledging that ghoul vampires are vampires, but that seems like pure snobbery to me, rather than there being any real reason why a ghoul that's fed a vampire's blood and develops supernatural strength and a thirst for more blood isn't a vampire. Also the name 'Crypt Horror' doesn't feel right to be used in-universe, it's too vague a term for something very specific.
(Peripherally related, capitalizing in fantasy is tricky and I hate how inconsistent I've been with it. I've flip-flopped on what rule of thumb to use a bunch of times, early in the quest I didn't capitalize words like 'dwarf' and 'elf' because the word 'human' isn't generally capitalized, then I started capitalizing anything that doesn't exist in the real world, and now I'm going with 'upper case for sapients, lower case for everything else, and also for humans because that word looks weird to me if I capitalize it'. I also don't capitalize 'greenskin', which seems like the right call most of the time except when I have to refer to them and some other race in the same sentence - like the phrase 'Skaven and greenskins'. Ideally I should have just picked a rule and stuck with it, but I didn't notice I'd changed the first time until I'd written way too much with the newer rule for it to be reasonable to go back and edit the capitalizations. Hopefully I'm the only person this inconsistency is bugging the hell out of.)