The answer is of course, ALL THE OPTIONS!
Omake: Mathilde, for once, tells the truth
"Well Reiner, I would be happy to...... You know what. No."
"No?" the Lord Magister asked, "Well, like I said it is your ri-"
"No, as in I am not happy, and if we're doing this you and I, it will not be done by oblique references or double-speak. The full, unvarnished, direct, truth. That is what you will get."
Reiner Starke blinked, then leaned back in his chair. "That would be an usual but admittedly refreshing change of pace, if only for the novelty of it. By all means, proceed."
"It was a difficult time, personally for me. "Mathilde closed her eyes in remembrance. "The first reason that gave me the idea was probably my personal grief. Abelhelm, who is was in l-lo--luv" Mathilde banged the table in frustration, but forced herself to continue "who I was in love with had just died a pointless death that Sigmar could have easily prevented. Brother Kasmir was right there, but Sigmar did not respond. That useless snivelly little bitch of a wannabe god failed his one good purpose and failed to heal a loyal servant of both him and the Empire."
Lord Magister Reiner Starke was staring intently, but this revelation was hardly enough to put his finely honed mind off-track and so he kept analysing and picking apart everything that was being said.
"So you were grieving then. Your love had just died but why would that - ah. A Sigmarite institution."
Mathilde nodded. "Indeed. Why allow a useless god to make a promising institution equally useless? It was both poorly-timed pragmatism and revenge of sorts. But understand, Abelhelm quickly gained my regard and admiration at the beginning of my employment, and after once spending most of the day in my underwear right next to him while we waited for necromantic assassins outside to be dealt with... well, the heart of a young maiden falls quickly and hard under such circumstances. "
"I wouldn't know."
"Ah, I am certain he could even see my ankles! It was so thrilling! And then Sigmar had the temerity to take him away. Such can not be abided. You could say I have held nothing but the highest disdain for Sigmar and his fools since then."
Reiner was nodding along, resentful that due to his position he couldn't retreat behind something being 'too much information'. He'd asked for this. Quite literally.
And yet despite wanting nothing more than to stop listening, his mind was racing ahead and thinking of what the Lady Magister was not saying, and wondering what the true reason must have been that this confession, entirely genuine it seemed, was the lesser evil.
"Of course, " Mathilde continued, "It helped I had a much better God to count on. My oldest friend. " She held forward a hand with fingers crossed and Lord Magister Reiner quietly filed this latest fact into his mind while Mathilde continued,
"Someone who's meddling have saved me from death and disfigurement more than a few times and brought me no amount of embarrassments as payment. The only male in my life I could truly count on, before King Belegar at least. The best person to catch thieves are thieves themselves of course, so really, promoting any other god would have been blasphemy. And while He and I play pranks on each other where possible, outright blasphemy is something I will never do. Not to an actual God worthy of the title."
"Interesting," Reiner commented, "that you would be so open about it but it does expl-"
"Of course, then there are the Skaven to consider" Mathilde interrupted. "Skaven are a problem beneath every major city and the Wurtbad Watch was incredibly underarmed to handle them."
"Hold on. I know, I KNOW," Reiner emphasized, "that you were not read in to the conspiracy until much later. "
Mathilde was nodding along. "Yes, exactly so. That is what my memories tell me as well, but I must insist on the Skaven angle as well. Not sure why, but for some strange reason it makes sense to me even though it makes no sense logically."
Reiner massaged his forehead
"So we have your grief over your dead lover who was the Elector Count and who you say Sigmar did not save, leading you to disdain him and institutions dedicated to him, the Watch being the largest and most visible you could affect at the time. Simultaneously, you had your own God - not a mainstream one but still an accepted Empire God - worship of whom you were looking to spread because you felt Him a better and more fitting alternative. And that this was simultaneously a planned move taken under the umbrella of the Conspiracy of Silence, since Sigmar's church doesn't and cannot officially recognize the danger as existing, so a religious bend that could allow for the recognition needed to be implemented, despite the fact that at the time you couldn't have known this."
"Precisely. Of course the reason this was so mishandled by yours truly is... well, kind of an embarrassing one" Mathilde confirmed.
"Oh NOW we get to something embarrassing?" Reiner chuckled in reply.
Mathilde turned her eyes skywards and took on a dramatic tone. "I was young an inexperienced. It was my first time but no one was there to be gentle with me. It got messy and complicated and was ultimately extremely unsatisfying."
Reiner was too busy choking on nothing to give a proper reply.
"Do you know what it does to a young maiden, fresh out of school, in her first job standing next to the love of her life? Assault a line of undead, battlecries on your lips, greatswords swinging, hacking a defensive line apart for your comrades to come rushing in.... But nobody came. We fought, back to back, but nobody came. No one, except more undead. And we hacked and we slashed and we killed and we decapitated and then he got wounded first."
There was something brittle and raw in Mathilde's voice.
"I stood astride on top of my dying liege and love, fighting an endless swarm of undead, and nobody came. Not until it was too late, far too late. I stood by his side as news came of a Magister who had blown themselves up instead of being there to heal Abelhelm. I watched a priest of Sigmar call to that useless bastard with all his faith and not receive a reply. I watched as mortal medicine failed. I heard the last words of my liege. You know what I did then?" Mathilde asked.
Intrigued, Reiner bid her to continue.
Words poured out of her mouth, desperate and chocked, "Everyone else were like headless chickens, useless and directionless. So I took command of an army, his army, and gave them purpose and a goal. I finished the fight. I gave out orders that lead to thousand of loyal troops dying, in the name of cleansing the blighted necromancers. I sentenced one to death by pyre and smiled as I watched that damn heretic scream his last!" Mathilde yelled.
"Me, a fresh Journeywoman, with barely a handful of spells to my name and no experience of proper warfare or being a judge and jury. All of that in a few days, and no authority figure in sight willing to shoulder the burdens on my behalf or even offer a hug to a scared child pretending to be a big, bad wizard of the Empire."
Mathiled took a deep breath, and collected herself. "Look at me, a Lady Magister and still not entirely over it." She mulled for a moment. "So yes, in the immediate aftermath, I was not exactly at my best."
Reiner tapped his fingers on the table a few times, deep in thought, "Indeed, quite.... understandable. Regrettable. That is, hmm, quite a tale. A rather multi-faceted tale at that, but I suppose situations under the purview of our College tend to be more complex than usual. And given the circumstances, the outcome could have been far less optimal."
There was a brief moment of silence.
"So, Mathilde. The complete and unvarnished truth you said. I am inclined to take you at your word on this particular occasion." Reiner shook his head. "If after all that, it was just a cover for some deeper secret, then I cannot make a realistic guess at it and would probably dread to hear it."
Mathilde gave it a moment of thought. There was that one tiny itsy bitsy teensy detail she hadn't mentioned. And, well, she'd promised the full truth, so....
"Well, " she said, upbeat, "Abelhelm did leave me with the genuine original edition of Liber Mortis that I've been carrying around until I read it and hid it in Karak Eight Peaks."
Lord Magister Reiner Starke was quiet for a brief second, before he sighed tiredly "You couldn't have at least made it believable?"
"I did promise the truth."
"Please just... get out. and work on your sense of humour."
Mathilde smiled and rose from her chair.
"Of course. Until later, Lord Magister."
Huh. Oh well, now the Grey College couldn't claim they hadn't known about Liber Mortis, if it came relevant in the future, so that was a load off.
Trying this 'Truth' thing was pretty nice.