Note that in Hungarian (which Fenarian is based on), bölcsesség means "wisdom". It is therefore reasonable to conclude that Bölk is the same horse that Fenarr rode into Faerie, since Paarfi records that horse's name as "Wisdom". See also below.
Note: Caveat Lector — some of this may be a bit tentative.
At some point in the past, Bölk was allied with Verra, the Demon Goddess in some endeavour. We do not know exactly what this was, but it might very well have had something to do with the founding of Fenario itself. As we see in the beginning of Brokedown Palace, and at the climax of The Phoenix Guards, a táltos horse — a horse named Wisdom — dies (apparently) while defending Crionofenarr, who is remembered as Fenarr in Fenarian legend. Bölk does say that he remembers Fenarr, but his statements are phrased with a certain ambiguity, referencing the changes in himself and the land since then. Both of the accounts mentioned above conclude with a peace treaty being agreed between Fenario and Faerie (the Dragaeran Empire), but we later see that the Fenarian story continues with the Demon Goddess pledging her aid to the kings of Fenario, and the kings of Fenario in turn dedicating themselves to the Demon Goddess. Bölk's sacrifice can be seen as securing benefit both for Fenario and for the Demon Goddess, hence the tentative suggestion that this specific incident was the alliance alluded to.
There are more than a few Fenarian folktales interspersed through the larger story of Brokedown Palace, some of which reference a táltos horse, or sometimes a táltos bull. It may be that these were all somehow incarnations of Bölk. Bölk does mention that he's been reincarnated 37 times before, and that he was at one point a bull.
Bölk first meets Miklós by the shore of the River out of Faerie. After introducing himself (much to Miklós' astonishment) and conversing for a bit, Bölk inquires as to Miklós' plans. When Miklós decides that he must visit Faerie, Bölk offers to travel with him at least until the border mountains, but insists that he, Bölk, cannot enter Faerie with him, saying that to return to Faerie, one must embrace it, and that he in fact rejects it. Bölk also states that once he was stronger than the power of Faerie, but that Faerie is now stronger than him. As they travel, Miklós wonders that Bölk does not seem to eat, and Bölk explains that he is "fed by the use folk such as you make of me" — and given the circumstances, he may well starve for hundreds of years (although he does not seem particularly discomfited by this). Finally, they reach the mountains, and Miklós leaves Bölk behind and enters Faerie.
Bölk then meets Miklós again by the shore of the River, at nearly the same spot as their first meeting, some two years later, after Miklós returns from Faerie. Miklós nearly attacks Bölk because of fear and surprise, but Bölk asserts that the Power of Faerie cannot harm him. Bölk also notes that he has changed a little in the past years (his coat being darker, and his body grown thinner), but adds that he in fact is always changing, and had in the past been a bull.
Miklós and Bölk then discuss Miklós' troubles with his brother, King László. As they are talking, Brigitta arrives to warn Miklós of pursuit. Once she joins the conversation, it quickly becomes clear that the two humans hear Bölk saying very different words. Prince Andor and the wizard Sándor arrive shortly afterward, and the obvious multiplicity of what Bölk says (or perhaps what each of them hears) increases even more.
It is clear, however, that whatever Sándor hears enrages him, to the point where he is moved to threaten Miklós. Bölk moves so that his shadow falls on Miklós, and Sándor's sorcery has no effect. When Sándor turns his attention to Bölk, Bölk responds by physically kicking Sándor in the head.
After Andor and Sándor stumble away, Miklós tries to understand what just happened. Bölk gives a vague explanation about different people hearing with different ears. They then speak of the Power of Faerie, and Bölk says that the Demon Goddess is a manifestation of that power — and that he, and Miklós, must consider themselves in opposition to the Demon Goddess. Bölk explains that while he cannot oppose the Goddess himself, he can be a weapon on Miklós' behalf. Miklós tells Bölk of the Tree growing in the room that used to be his, and they both decide that they must return to the Palace in order to investigate what it is.
When they arrive at the Palace, Miklós has Bölk taken to the castle stable. Miklós makes up with László, and later visits Bölk with Vilmos, and once again, the two men hear the horse saying different things. Later, László and Sándor visit Bölk as well, and for once, we see just how different those words can be: Bölk always sounds friendly and polite when speaking with Miklós, but László and Sándor hear him being rude, contemptuous and violently threatening (he introduces himself as Death, and states bluntly that if he enters the Palace, he will be the end of the King, and of Sándor). Unsurprisingly, Sándor feels it necessary to try and bind Bölk, using sorcery to tie him up in a massive knot of ropes.
When Miklós finds Bölk in this state, he is enraged, but Bölk demonstrates that the ropes are no problem, and snaps them all almost effortlessly. Bölk also tells Miklós that he was bound because he asked László to justify his reliance on the Demon Goddess — definitely not what we had just seen László and Sándor hearing. Bölk calms Miklós down, and they discuss the Tree again.
After the collapse of the Palace floor, Miklós visits Bölk, and tells him that he is ready to act. They discuss the Palace, and Bölk convinces Miklós that, unlikely as it might be, the proper course of action is to attack the Demon Goddess. They leave the stable, and advance on the idol of the Demon Goddess in the courtyard.
Bölk kicks in the knees of the statue — which effort causes him to become unusually exhausted, considering how indomitable he has appeared to be until this point. The statue falls, and the Demon Goddess appears. She recognizes Bölcseség, calling him by name. She then speaks, regretfully, of how she must now kill Miklós. However, when she attacks, Bölk jumps into the path of her bolt of power, and has a huge hole blasted from his side.
As he lies dying, Bölk tells Miklós what to do next. Miklós, following Bölk's request, cuts out Bölk's heart, and flings it into the Demon Goddess' face. She makes most of it disappear, but a few drops of blood reach her face. She screams, collapses, and dies, and her idol crumbles.
During the final confrontation between Miklós and László, László attacks Vilmos with Állam. Desperate, Miklós reaches into the Tree, and finds a huge, heavy branch, which he pulls out and gives to Vilmos. When Állam strikes this staff, the sword shatters, and László is defeated. When Miklós examines the staff, he sees that one end has been carved into the shape of a horse's head, which opens its eyes and speaks to him with Bölk's voice.
Bölk explains that this is now his thirty-eighth incarnation, and that he can no longer feel, since his heart has been removed. When he speaks now, everyone who can hear him hears the same words. Bölk somehow knows that Brigitta is pregnant with Miklós' child, and tells them all. When Brigitta leaves because of this, Bölk advises Miklós to busy himself with helping Vilmos, who is now the king, in rebuilding the Palace and ruling Fenario.
As far as we know, Bölk is still in the form of a staff, and is advising King Vilmos (or Vilmos' heir).
- Miklós - friend, master
- Brigitta - friend
- Vilmos - current master
- Verra - former ally, more recently, an opponent
- "The more tightly I am bound, the harder I am to contain."
We have strong reason to think that Bölk is probably a Demon (definition #3), because
- when Bölk speaks, different people often hear different things, implying that he is manifesting multiple instances of himself
- Bölk appears to be oddly passive, unable to do certain things on his own behalf, and actually requiring someone (a "master") who can use him - which certainly looks like he is controlled
- Bölk claims that he feeds entirely on the use his master makes of him, and starves when he has none.
However, the possibility that he is a God, or something else entirely, cannot be ruled out. Bölk's own statements about himself are not entirely clear.