As the last post, design principle for Terrae Vertebrae was that initially that the races elder to humanity all balance against one another; see libertarian Dwarves, community-centric Elves. But I lacked a proper balance against Fauns and Satyrs (Caprines). I had invented them as a Gnome substitute, but since associated them with the 'Southern Influence' of C.S.Lewis's The Pilgrim's Regress (which is a blasted odd thing to grasp at for Character Alignment, but there you are).
What balances Caprines? Speculations at the time included Dvergar, Hrossa and centaurs. Thinking about it now, a Marshwiggle would make a good contrast: deriving from Lewis, known for their gloom, enduring of the cold and ultimately, disciplined and logical (consider Puddleglum's role in the climax of The Silver Chair). [See also comments to this; the Caprine, as 'not a Gnome' is also 'not a Halfling'].
But creating a Northerner or Anti-Caprine class that slots into a putative 'Proto-Vertebrea' setting as a Prophet replacement requires a bit of mythological heft - which knocks out the Marshwiggle for this role (though by no means out of the picture altogether).
All caught up? Now, read on....
Dvergar are too similar to Dwarves. Hrossa, as Marshwiggles, lack that heft. As the title suggests, I think centaurs are the solution.
'But' says the Classically educated reader 'Centaurs are violent and savage, despite exceptions. They are unsuitable as a Regress-Northern species. Besides, they have a basis in Greek accounts of horse-borne nomads, set against the static and agrarian Greek city-states. Not quite Northern. This will not do.'
These are not unreasonable arguments against the centaur as the Anti-Caprine. However, my influences are relatively widespread.
First, consider the horse as a symbol. Yes, the wild horse is most Romantic and spectacular. But the horse as known to Western civilisation is a draught animal; hardly the lowest beast of burden, but not one let to roam free either. The horse's might and splendour is seen as something that is governed, and enhanced by being governed. Consider the uses of the horse in the Equestrian Portraits of Charles I.
Think also of the chariot and the stagecoach: horses - more than four, even - cooperating in drawing the burden across the countryside. Mention of the Chariot draws us nicely to the Allegory of the Chariot. Horse(s) and Man together are the (civilised) Human Soul. This is not the only link between the Rational and the Equine: consider Gulliver's Houynhnms - Rational to a fault and certainly inimical to humanity. Orderly and peaceable beasts, to be sure - but not altogether pleasant ones. Let us not forget that Lewis conjured the Northern as a diversion from the true course.
[A game for those of you who wish amusement: watch an episode of Star Trek and mentally replace every mention or appearance of Vulcans with Houynhnms.]
Speaking of Lewis, let us not neglect our Appendices N. Much twentieth [-first] century literature conjures the centaur as a wise teacher (every dwarf is Gimli; every centaur is Chiron). Narnia is an example; Harry Potter another.
What is more, the Northern temperament in The Pilgrim's Regress is not opposed, as such, to savagery or indulgence - even if austerity is one manifestation of it. The giant 'heroic nihilist' Savage feasts and drinks (from the skulls of his enemies, no less). Among his followers, one tribe is listed as 'Gangomani' (others being Marxomanni, Mussolimini and Swastici). Given the Northern temperament and the time of writing, the persons conjured are more likely the loyal triggermen of Capone-esque mob bosses than desperate muggers and school drop-outs. The Gangster, as conjured, is hardly teetotal or celibate - but rather indulges his passions at a given moment. Consider the stoic, cold maxim of Coppola's The Godfather: "It's not personal. It's strictly business."
So, yes, you can do a Marlon Brando impression as a centaur mob boss and not have be out of place. Moving away from such a specific genre trope, the 'work hard-play hard' culture would not be unfitting for a Regress-Northern character. Indeed, if the most Regress-Northern one can be is somewhat like Savage, the most 'centaur-esque' centaur need not be unlike the violent, rapacious classical centaur.
Having taken you on that little journey, let's descend back to a firmer footing. What does a Fifty-Two Pages centaur class look like?
HP - d6+1+ CON +/-.
Attack Modifiers - None, initially
Mind Save 7 + WIS +/-
Speed Save 5 + DEX+/-
Body Save 7 + CON +/-
Knowledge Notice Detail Hear Noise Handiwork Stealth Athletics
[XX] [ ] [X] [ ] [X] [X]
Starts with one extra Language, and Spells: 2+INT bonus.
Level Advancement: +1 Melee, +1 Missile every Fourth Level
+1 to all Saves every Odd Level
+2 Spells per level
Centaur movement is as a Heavy Warhorse; that is, 15. However, climbing or anything that involves gripping with the feet is more difficult. Even a simple obstacle counts as Hard.
Spells cast as Prophet. A Centaur, as Regress-Northern belongs to "rigid systems whether sceptical or dogmatic, Aristocrats, Stoics, Pharisees, Rigorists, signed and sealed members of highly organised 'Parties'." This limits their spell choice, just as a Prophet's faith does.
Likewise, it gives them a 'sacred' weapon. There is a weapon emblematic of their creed; one they are trained or accustomed to use. To return to the Gangster-Centaur, this may merely be that Our Gang uses Baseball bats and The Gang the Next Block Over uses straight razors. (This starts to sound less like The Godfather and more like The Warriors).
Centaur encumbrance, as a dwarf, is as a STR 18 character. However, a third of these slots must be packed and unpacked by another character. (The human torso cannot turn 360 degrees.)
A Centaur can be ridden as a horse (though there may be taboos about this). However, it encumbers (as riding a horse) and may interfere with the centaur's abilities.
Much as Half-Giants, for armour to count as full-body, it must be built for a centaur. A humanoid mail-shirt (or similar cuirass) can be worn, but counts as Partial.
I am not an equestrian myself and have concentrated in this post more on cultural ideas than biological ones. Readers may wish to examine the SFF and Equines column from Tor Books. There are even some centaur specific posts, with this convenient diagram.