Old-School saving throws tell you against what you are defending; the “how” is left to your imagination.

Like everything in these games, saving throws are a mechanism and not a narrative; the player rolls the dice and the player or referee interprets the result (success or failure) according to the context, or he can ignore the interpretation and it doesn’t matter, the game moves on.

For example, an attack roll doesn’t represent the same in all cases; if successful, it can represent different forms of attack and defense made in a round: thrust, feint, riposte, swing, parry … The important thing is that the dice tell you if you succeed or not, whereas the form of the attack (the “how”) is irrelevant. It’s up to the players to describe it or ignore it and move on with the adventure.

The same applies to saving throws.

While, since 3e, the saving throws tell you the “how” (a reflex save meaning that the character throws himself aside to dodge an attack, a fortitude save meaning the character receives the attack but resists it as would a boxer being punched, a willpower save meaning … well, who knows what the hell it means, that your soul is hard as steel, perhaps?*), old-school saving throws are a mechanic to represent what you are defending against and what are your chances of success, leaving you the responsibility to describe the way your character does it (a responsibility, however, completely negligible).

Thus, we have the 5 categories of old school saving rolls, specifically Basic/Expert Sets (B/X, BECMI), and most OSR retrcolcones, like Labyrinth Lord and Old-School Essentials:

Death Ray or Posion

Magic Wands

Paralysis or Turn to Stone

Dragon Breath

Rods, Staves or Spells

And these are the categories of AD&D 1e:

Paralyzation, Poison or Death Magic

Petrification or Polymorph

Rod, Staff or Wand

Breath Weapon

Spell

And, just for fun, those of LotFP:

Paralyzation

Poison

Breath Weapon

Magical Device

Magic

Although the categories vary from one version to another, the mechanics are identical: you make a saving throw when you are in imminent danger. In normal combat, if an enemy attacks you with his sword, your AC protects you, which not only represents your armor, but also your ability to defend in combat.

But in the face of other dangers, such as a dragon that throws you fire, a basilisk that looks you in the eye, ingesting poison or being the target of a spell (or magic wand), your AC (defense capability plus armor, remember?) does not come into play, but you still have a chance, even if it is small, to avoid damage.

Save Versus Something

Save versus Poison. The adventurer probably did nothing to avoid dying poisoned, the roll is passively successful, the reason he didn’t die can be anything from the poison having no effect or the creature failing to inject it to the adventurer being immune to this specific poison, even divine intervention, or maybe those luminous mushroomes he ate that morning neutralized all toxins.

In 3e, this saving throw would be a fortitude save, and in 5e, a constitution save (which come to be the same, actually). This can only be interpreted in one way: the poison didn’t kill the adventurer due to a powerful immune system.

Of course, the old-school allows this same interpretation, but not only this; it gives you the freedom to interpret the numbers as you see fit.**

Save versus Spells. A damn magic-user attacks you with a fireball. To avoid damage (or, well, half the damage), in 3e or 5e you must make a reflex or dexterity save, meaning that you dodge the fireball (the spell’s description makes this interpretation unlikely, though), but in the old-school we really don’t know how you do it other thank making a save versus Spells (i.e. we only know the mechanic, but we are not offered a narrative interpretation***); maybe the agile thief jumps to the side, yes, but think about that heavy fighter with full armor, can he really dodge? Most likely his armor protects him, but if the idea of a hot metal armor not causing severe damage bothers you, then you can say that he used his sword to deflect the explosion, or he punched the ball of fire like those Dragon Ball fighters do all the time.

Now imagine that you are on a cliff, there is no space to dodge without falling from a great height (and no doubt die), but anyway you make a successful saving throw. Did you dodge the attack? I don’t think so. In the case of a magic-user or an elf, it’s easy to imagine that they know a mystical handsign that works to counter or deflect a spell, reducing (or denying when appropriate) its effectiveness.

The thief and halfling are lucky and that strange, outer, chaotic force known as luck interferes with the spell, reducing its effectiveness. A cleric is protected by his faith (which is another form of magic, or anti-magic if you consider magic as something unholy). The fighter, like the dwarf, relies more on his instinct, his strength, his ability, and in general “sheer defiance”, all of these tangible or demonstrable things, not abstract, philosophical things like magic, and that confidence makes them face magic with disdain, reducing its effectiveness.

* It doesn’t matter, the game moves on.

** Of course you can interpret 3e and 5e saves in any way you see fit.

*** To be honest, 1e offers both a narrative option (“Defensive Adjustment refers to the penalty or bonus applicable to a character’s saving throws against certain forms of attack [such as fire ball, lightning bolts, etc.] due to dodging ability.” PHB, p. 11) and the old-school option (“If some further rationale is needed to explain saving throws versus magic, here is one way of looking at it … A character under magical attack is in a stress situation, and his or her own will force reacts instinctively to protect the character by slightly altering the effects of the magical assault … So a character manages to avoid the full blast of the fireball, or averts his or her gaze from the basilisk or medusa, or the poisonous stinger of the giant scorpion misses or fails somehow to inject its venom. Whatever the rationale, the character is saved to go on.” DMG, p. 81)