Subtle magic is a funny thing. Just watch Apollo Robbins work his craft removing watches from people at parties, and you have to marvel at it.
Of course, such subtle magic cannot be overt. If everybody could see it was magical, it would fail to qualify as subtle. Thus we see the first rule: "the staff must give hints to the wielder that it is magical in a way that is hard for a third party to observe." An obvious answer would be a loud booming voice in someones head announcing "you have a magic staff, let me teach you how to use it." But that hardly qualifies as subtle. Certainly not by Rynn standards.
Let the games begin, shall we?
Our staff has the clear necessity of helping its wielder unlock the staff's true potential, without overtly guiding them towards those ends. So it's going to have to rely on its greatest ally: patience. It's simply going to have to continually work with its new owner until one day the owner starts to put 2 and 2 together and realize the answer is at least 4.1, and seems to be going up every day.
The owner clearly has a will. Anyone wielding a weapon has a will they wish to impose on others, or else they wouldn't be wielding a weapon. The staff can patiently wait, sensing that will. When it sees an opportunity, it may do just slightly more, or slightly less than intended. If the owner strikes out, it may hit the enemy, even though the actual butt of the staff was just shy of a strike. Most staves are wood, flexible, but once in a while, it might flex just a little more than you thought the wood should be able to flex, allowing the staff to strike around a block instead of being stymmed.
In this phase, the staff is merely trying to make sure the owner realizes it is special. This phase continues until a key psychological shift occurs: the owner gives identity to the staff. Instead of thinking of it as "a staff," the owner begins thinking of it as "this staff," a unique individual. The owner might even choose to give it a name. Regardless, once the staff has an identity in the owner's mind, the staff has a beachhead to begin the real work of teaching the owner how to use it correctly. The staff may begin to display emotions. It may communicate ("My staff feels sluggish today... perhaps today is not a good day to fight. We should rest instead."). Such "illusions" of personality are not unusual for fine weapons, so nobody besides the closest co-horts of the wielder would even notice. Even they would just think the wielder is a little nuts.
In fact, those illusions show up in so many myths, it really leaves one to wonder, doesn't it?...
Once the wielder has admitted a personality to the weapon, we can begin the final dance between weapon and wielder. Now that we have two personalities in the mix: a wielder and a weapon. Now we have a solid back drop to build the real training upon: social interactions between individuals. Maybe it shows up as the wielder just "knowing" what the weapon is thinking. Maybe there's a physical dance, where every single strike or parry conveys the spirit of the dance between weapon and wielder. Maybe the sanity of the wielder buckles, as he or she begins to hear voices.
In every step of the way, the weapon is going to need to earn its keep. If the wielder is going to be ridiculed for talking to his staff, the peanut gallery better be silenced when they see the wielder and weapon dance across the corpses of their enemies. Fortunately, a staff owned by Rynn would be up to the challenge. The wielder? That's another story. Since nothing is overt, the owner can't simply wield the staff "to great victory." That would show off obvious magic. Instead, the two individuals need to work together. The wielder needs to get used to being told where to stand, just like the lead in a dance needs to have a subtle sense of where the follow would like to flourish. A strong individual will appreciate this dance, and never let their partner go. A weak individual... well...
The lead has to be strong, but able to listen to the spirit of the follow. If the lead is not strong, the dance crumbles. If the wielder cannot be the lead, because they are not strong enough to keep up with the needs of the staff, Rynn's staff will be more than willing to oblige the wielder, and become the lead. In such cases, madness would surely follow, but the madness would never quite cause destruction until a time suspiciously convenient for the staff to find a new wielder.
Alex's lungs burned with exhaustion as the staff hummed with vibration from the force of the last blow. All eight royal guards that had been sent to escort him to the prisons lie at his feet. Two were still breathing; it almost felt as though the staff still had a purpose for them, still vibrating to its own tune -- imperceptibly unless you looked hard or listened carefully. The remaining witnesses, Alex's companions in crime, had long since fled. They had fled not from the royal guards and the summons they brought. The gang Alex rolled with was far too loyal to leave one of theirs behind. But when the first guard began spurting blood, layrinx collapsing under a blow so fast that neither gang member had even realized the staff was inexplicably in Alex's hands, they fled. They had seen Alex take a life before, but not like this. Not like this.
Alex coughed, a spasm of pghlem and a little blood. No guard had struck him. Heck, only the last had had the time to even take a full swing at him -- folly, at that. Alex readjusted himself. It wasn't easy getting used to striking so furiously that even his own organs struggled to keep up with the demands placed on them. His staff knew where he needed to be, it was Alex who found himself constantly the weaker party, the party struggling to catch up.
"I swear, if I knew half of what this staff seems to know, I'd have no peers," he muttered to himself, feeling his arm ache. The vibrations from the strike were still surging through the staff, like the vicious sting of a bat struck against a rock or a wall. It ran up and down his arm, though he did nothing to extinguish the vibrations. Alex felt it would be rude to the staff, like he'd hurt its feelings if he tried to take back control of his arm once more, removing it from this ringing.
Alex heard the two living guards whispering. No, no. That wasn't quite it. It was definitely more than just two voices. Alex dropped to his knees. The auditory hallucinations of his dead foes wore on him, moreso after every fight. Dropping to his knees in submission seemed to be the only thing that had any effect on their prattle as it rose from a whisper to a shout. He held fast, on his knees, vibrating staff in hand, waiting for the voices to end. And they did.
What replaced them was far more sinister than the taunts and goads of dead warriors. Their voices were replaced in an instant, silenced, to let one pure voice ring through. Her voice was almost melodious, smooth, without a hint of malice. And yet what she had to say was more than Alex had ever had to bear.
"I have decided to accept you as my student," she purred, as calm as though there were no corpses piled up around them. "You should know what that means." The pain from the vibration in Alex's arm diminished, and he focused more on this new voice. It was this, or eternal madness, he decided. Better this.
"You should know what this means, Alex. It means I will have to break you. It means I will break you. You are my student now, so it must be."
"So it must be."
A short while thereafter, an Alex gathered his stuff and headed East, towards the town. He would meet up with his friends there. There would be words. Alex breathed easily now. The worst was over, or so he tried to tell himself. He knew it was a lie, of course, but it was a good lie. He sighed effortlessly, walking away from the pile of eight dead royal guards - walking away from the small pile of his phlegm and blood slowly seeping into the dirt. He took a breath, pondering what an autopsy on two of the guards would reveal: lung damage that could only be explained by a tremendously lucky blow to just the right spot on the sternum, through the armor plates. He took another breath, thinking just how lucky he was that his lungs might heal so quickly after he hurt them so badly. Lucky, Lucky, Lucky.
A third breath, and they was gone.