Lem knew better than to give the sort of demonstration that would put Lady Nassau's life (undeath?) in danger, much as he wanted to prove his effectiveness by putting a stake through her chest. Unfortunately, the same power that bound a thrall to their master also prevented them from actively attacking their masters.
It didn't prevent indirect attacks, at least as far as Lem knew. Rumors always circled about Thralls who had forced silver into their own veins, in order to feed their masters their own tainted blood. Other tales included creating weak points in the darkened windows, leading to their eventual shattering, allowing sunlight to pour into the homes and bedrooms of the vampires who owned them.
But Lem didn't have the opportunity to try his hand at any of these actions. For one, he wasn't the sort of thrall that was usually fed upon - he was a weapon, and his value lay in his ability to fight as a representative of his master, far more than his ability to produce blood reliably. Weapons' blood was spilled in part because it was less palatable to vampires. Lem wasn't sure if this was caused by the weapon's binding magic, or if the binding magic sensed the blood's inpalatable nature and designated them weapons because of it. In any case, it was rare for a vampire to feed on a weapon thrall - though never impossible, and one could never allow their guard to slip around a vampire. Even a meal as unappealing as a weapon could still tempt a sufficeintly desperate member of the Blood.
"Daggers are a somewhat unique tool," Lem began, withdrawing two of the daggers he'd taken as he spoke. He twirled them around his fingers, careful not to knick himself with the blades. "They are useful for both distant and close-range combat, and with proper training, can be used for both at once."
Lady Nassau looked genuinely interested, which Lem supposed was in part due to her upbringing. Weapons were a common form of entertainment. No small part of that entertainment was due to the ever-lingering question of who would draw first blood, and if the weapons would survive the combat they'd been forced into. "How so?" she asked, gesturing at the daggers in Lem's hands. "Once you throw them, they're gone, and if you need them for close range, how would you use them for a distant foe?"
A question Lem had asked himself, once. Before his mother had taught him a thing or two about magic. The first thing she had taught him was that magic could not be commanded, not by humans. Even mages studied for years to so much as negotiate with the potent force that formed the nexus of all power in their world. For creatures who were magical by nature, such as vampires (particularly those of the Blood), fae, and were-creatures, they had a much easier time, in no small part because they had a solid connection to magic within the very core of their being.
This, his mother had whispered, in the quietest hours, when the sunlight barely crept in through the cracks in the windows, was the true strength of the thrall. For like those other magical creatures, thralls, too, had a strong tie to magic. The same binding that kept them enslaved to their masters gave them a unique bridge to tap into the power of magic itself.
Not that it was wise to flaunt such an ability. And as a weapon, Lem had never been much for studying or learning the many ways magic could be plied and prodded into meeting his will. In truth, Lem didn't particularly like forcing magic to do anything that it was disinclined towards. Lem himself had been bound and forced to act in a manner that was in opposition to his will far too many times to feel comfortable doing likewise, even to an unintelligent part of nature. If magic had a will of its own - and many firmly believed it did - then Lem had no desire to subsume that will.
That didn't mean Lem couldn't ask for a favor here and there. And, as luck would have it, magic often seemed inclined to grant him a boon.
So, when Lem turned to Lady Nassau, he had complete confidence in his ability to pull off the trick that he and magic had been perfecting for years. "Perhaps a normal dagger, yes," Lem smirked. "But these are special." It wouldn't do to let one of the Blood know that their thrall had discovered the power of magic. Lem in particular would be under scrutiny, given who his mother was. But no one thought twice once Lem suggested that his daggers might be magical. That perhaps there was an enchantment woven into them. He didn't understand how they couldn't see them, when to him magic was a strong and present force that danced under his skin and whispered through his hair, sparking and dancing in the corners of his eyes when it grew particularly fierce. Yet no one ever seemed to notice that the daggers he used were totally mundane. It was magic itself that lent its hand: not through layers of enchantments that mages had worked long and hard to contractually arrange with the underlying force of the world, but through Lem's binding. Lem was a weapon. The trick was letting magic know that he didn't mind serving two masters, if magic wouldn't mind lending him a little power in exchange.
Lem turned, throwing one of the daggers one direction, then spinning around and tossing the other the opposite way. They flew straight and true, and when he flicked his fingers, they came right back to his hands, just as magic loved to do. Playful and mischievous, as magic often was when Lem asked it to help him, one of the daggers barely clipped one of the long, flowing locks of knowledge Dav, giving one side of his head a lop-sided trim.
Lem shot him a not-too-sympathetic look. "Apologies, Knowledge Dav," he said. "The daggers sometimes have a mind of their own."
Lady Nassau was eyeing the daggers with new appreciation. "That is exquisite craftsmanship," she said. "Usually I can see the threads of enchantment that tie any sort of magical tool to its caster's hand. But in your case, it almost seemed as if magic itself plucked them out of the air to return them personally."
Lem felt his eyes widen before he could catch his reaction. She could see enchantments? All the time? Even Lem could only see magic when it was at its most potent. He felt it, more than saw it. Almost instinctively, he felt his own eyes rise to meet the blood-red gaze of Lady Nassau. The burning intensity there burrowed into his chest, squeezing like an iron fist. "Is that so?" he said weakly, managing to tear his eyes away and glance down at his daggers, forcing a laugh that could not possibly sound genuine. "I suppose they're more valuable than I realized."
"Hm," Lady Nassau said thoughtfully, her voice soft. "Perhaps something in this room is."
It was quite clear to Lem that she did not mean the daggers.