10 Differences Between Old-School Essentials and Other Games You Might Have Overlooked

Rules you might have missed, whether you're new to OSE or a veteran of the original 1981 game.

Illustration by Howard Pyle, 1903

If you have played other D&D-style games, it can be easy to miss that Old-School Essentials (OSE) and the 1981 rules it’s based on handle certain terms and situations differently. Of course you can change any rule you wish. But knowing the rules allows you to make an intentional and informed choice.

I’ve been running and teaching players OSE for a few years now and here are some rules that both players and referees can easily miss while flipping through the rulebooks. I discuss how I interpret these rules and any house rules I use. Some of these rules are essential for OSE play. Others are not but I find all of them worth trying out.

Summary

1. A prime requisite ability score (such as Dexterity for a thief) may be increased by lowering another score during character creation.

2. A turn represents 10 minutes while a round represents 10 seconds.

3. Room traps and treasure traps are handled differently.

4. Infravision works differently than darkvision from other editions.

5. The referee rolls when PCs attempt to listen at doors, hear noises, hide in shadows, move silently, or find room or treasure traps or hidden doors. The die result is kept secret from the players.

6. Players must declare spells and movement in melee before initiative is rolled each round.

7. The dexterity modifier is not applied to the damage roll for missile weapons, only to the attack roll.

8. Natural healing requires 24 hours of uninterrupted rest rather than 8 hours.

9. The identify spell doesn’t exist. The properties of a magic item is identified by using it or by hiring a sage.

10. Experience points are only awarded when the PCs return to safety.

1. Players can increase one ability by lowering another at character creation.

During character creation, after rolling ability scores and choosing a class, the player may increase a prime requisite ability for that class by 1 by lowering STR, INT, WIS, or DEX by 2. An ability may not be lowered by low 9 this way.

Many editions of D&D with random ability scores don’t have a rule like this. It adds a little bit of customization to otherwise random ability scores. It also increases the chance of having a high ability score.

I recommend doing this if your prime requisite ability is just shy of receiving a higher modifier. Increasing a fighter’s STR from 12 to 13 or from 15 to 16, for instance. This will improve the fighter’s melee attacks and increase their experience point bonus.

Many sets of random ability scores won’t have scores high enough for this. For instance, that fighter’s INT, WIS, and DEX might all be 10 or lower. One would need to be at least 11 in order for it to be lowered to raise a prime requisite. And for many character’s won’t have any abilities at the cusp of a higher ability modifier. Others may not wish to sacrifice any ability scores. But it’s a nice rule to take advantage of when it makes sense to do so. I think of it as a character becoming hyperspecialized at the expense of their other abilities. A warrior who neglects the books for instance.

2. Turns and rounds

Turns represent 10 minutes. Turns are usually used to measure time spent in adventuring locations outside of combat. Rounds represent 10 seconds. Rounds are usually only for measuring time in combat and similar situations. An effect with a duration of 6 turns lasts an hour. Turns and effects that are measured in turns should be tracked, such as with the turn tracker from Necrotic Gnome. I recently found another example in the adventure clock from B11 King’s Festival, which has the benefit of numbering the turns, which I wish Necrotic Gnome’s did but I think the latter tracker is more useful overall. I’ll have to make my own.

The adventure clock from B11 King’s Festival.

3. Room traps and treasure traps are different.

Room traps and treasure traps are handled differently. Room traps can be triggered by anyone entering an area. Treasure traps affect those who tamper with or steal an item. Any character may search for a room trap but in OSE Classic Fantasy dwarves rather than thieves are best at detecting non-magical room traps. Thieves are the only class capable of finding and removing treasure traps and have no special ability to deal with room traps. (My interpretation: I rule that anyone can discover and disable any trap if their player describes taking actions that would logically lead to the trap’s discovery or disarmament. But I allow rolls to be made as a fallback.)

4. Infravision is not darkvision.

Infravision is not the same as darkvision, the ability found in more recent editions of D&D. Infravision allows a character to see heat and is disrupted by visible light and large heat sources. Torches and lanterns disrupt infravision. Infravision does not allow a character to see better beyond the edge of firelight (unlike darkvision in 5th edition). Infravision works like infrared imaging technologies, including thermography, and is similar to the thermal sensing ability of some snakes, vampire bats, and some insects, while darkvision (as found in recent editions) works like light intensifying technologies and is similar to the night vision of cats and other mammals.

If darkvision works like a cat’s night vision, then darkvision shouldn’t work in the absence of normally visible light, since cats cannot see infrared light contrary to how darkvision works in 5th edition. But infravision works as long as heat, and therefore infrared light, is present. Both darkvision and infravision should be able to be blinded or dazzled by too much visible light or too much heat, respectively.

In Old-School Essentials all non-human monsters are assumed to possess infravision that works out to 60’ feet unless their description indicates otherwise.

The above distinctions could be seen as overly based in science for a fantasy game but I personally find applying consistent logic based on animal night vision can increase immersion and improve my descriptions of what characters with these abilities can sense in the dark.)

5. Referee rolls if the PC wouldn’t know the outcome of a check.

The referee rolls for PC thieves attempting to hear noise, hide in shadows, move silently, or find treasure traps. The referee should not tell the player the results of the roll. The PC believes they are moving quietly, are well hidden, or able to hear. The referee should also roll for any PC who is listening at a door.

The referee should also roll checks when any PC attempts to listen at a door, search an area for secret doors and room traps. Only if the roll is a) successful, and b) finds something hidden should the referee reveal that the roll was successful. If either of conditions are not met, the referee should keep the result of the roll secret so players don’t know whether they a) failed and missed something or b) if nothing is hidden in this area.

Each character only has one chance to listen at a door or search for a particular secret door or trap. Multiple PCs can increase their chances by searching the same area (one roll for each character).

(House rule: I allow characters further attempts to listen at a door or search for something if PCs spend an additional turn per extra attempt, but they still don’t know if they didn’t hear anything the first turn because they failed or because nothing is emitting sound. This requires them to spend more time in the dungeon, using up more light, and increases the chance they encounter wandering monsters.)

6. Spells and melee movement are declared before rolling initiative.

Players must declare the intent to cast a spell or to move while in melee before initiative is rolled each round. If a spell caster fails a saving throw or is attacked successfully before their side casts spells that round, their spell fails and they forget the spell, as if it had been cast.

If the opposing side goes before the players’ side, they may have an opportunity to disrupt the spell being cast, by successfully attacking the spell caster or by causing an effect that requires a saving throw. This can also be used by PCs battling enemy spell casters. I’ve seen low-level characters disrupt a lich’s spell casting this way.

The two options for moving in melee are retreating and making a fighting withdrawal. Retreating has the advantage of allowing the character to move up to their full encounter rate but at the cost of not making an attack and opponents gaining a bonus to hit the retreating character. A fighting withdrawal allows the character to attack but the character may only move up to half their encounter rate.

7. Dexterity doesn’t affect missile damage rolls.

Dexterity Missile modifier does not apply to damage rolls with ranged weapons, only to attack rolls. This is unlike the Strength modifier, which applies to both melee attack and damage rolls. Melee attacks tend to be more damaging than missile attacks for this reason and, if you are using variable weapon damage, because their damage dice are often larger.

8. Natural healing takes 24 hours, not 8.

Natural healing occurs after 24 hours of complete and uninterrupted rest (not after 8 hours). At the end of the 24 hours, a character or monster restores 1d3 hit points. (House rule: Resting in comfort or in the care of a healer increases the hit points regained. Resting in poor circumstances either prevents any healing or reduces the number of hit points restored. An eight-hour rest also heals a single hit point in my games.)

9. The identify spell doesn’t exist.

The spell “identify” does not exist in Old-School Essentials. The properties of magic items are usually identified by trial and error or by consulting a high-level NPC magic-user. Using a magic item allows a character to identify it automatically unless its description says otherwise, as in the case of some cursed items that do not reveal their curses until specific circumstances arise.

10. Experience points are awarded upon returning to a safe area such as a settlement.

Experience points are awarded only when the party leaves the adventuring area and returns to safety. This includes XP for recovered treasure and for defeated monsters. I interpret “returning to safety” as returning to a settlement but I would define settlement loosely in some cases. A secure camp of allied outlaws could suffice. Joining a friendly caravan of nomads for a time might too. As long as the player characters can rest comfortably and conceivably stay for a few days or a week with few worries (this doesn’t mean intrigue can’t occur).

Conclusion

Old-School Essentials challenges some of the assumptions of later editions of D&D, especially the 3rd, 4th, and 5th editions. The rules may even differ from the memories of people who played B/X D&D in the 1980s. When you store many iterations of D&D, not to mention house rules, in your memory, it’s easy for them to blur together. Plus, every table interpreted rules differently and prioritized different rules.

All of these rules can be impactful on play. I hope new and returning players to OSE and its ancestors find this overview of some of its distinctive rules useful.