In MyD&D the bonus of a magic sword was generally used to indicates the Grade of the weapon. So a +5 weapon was Grade A (or First Rank), a +4 weapon was Grade B (or Second Rank), and so on down to a +0 weapon being Grade F (or Sixth Rank). Over time, the Grade of the weapon became more important in defining the power and abilities of the weapon than the numerical bonus.
I was always a little unhappy with Gygaxian approach to magic weapons, mainly because a +1 bonus was a miniscule effect when you used a d20 to resolve combat. The original Chainmail approach used 2d6 instead, where a +1 bonus created a much more sizeable bonus because of the normal distribution of the 2d6 roll. On Chainmail and OD&D, 75% of swords were +1, and the maximum bonus for legendary named weapons was +3. That 2% chance of a +3 sword was supposed to represnt finding magic swords such as Excalibur, Gram and Durandel. In MyD&D these have always been represented by the legendary Grade A (+5) weapons, which must be named and have a dedicated purpose.
In the MyD&D grade system a Grade F (+0) weapon is effectively a masterwork weapon. It gives no actual bonus in combat, but is a status-boosting item for characters, increasing the character's perceived fighter level by the magic bonus of the craftsman. So a masterwork weapon produced by 7th level weaponsmith would grant the wielder a +3 bonus to the characters Fighter level. As a side effect of their craftsmanship, a masterwork blade can be enchanted without shattering the blade when the enchantment ends.
Now there was only one type of Grade E (+1) sword in MyD&D. It traditionally provided a +1 bonus to the wielder (as well as the status bonuses of a masterwork weapon). This bonus was a result of the simple perfection of the sword rather than being the result of any overt entchantment. Now I consider this bonus to be inadequate for the idea behind the weapon. So my new proposal is that Grade E (+1) and higher swords be reclassified as a "magic sword" in MyD&D.
All magic swords in MyD&D will allow the character to roll two d20 and take the highest of the two results as the result of the roll (the same as for advantage in 5E).
The comparative chance of success for a normal person using a +1 magic sword is given in the following table.
| Armour Worn | OD&D Sword+0 | Chainmail Sword+0 | OD&D Sword+1 | Chainmail Sword+1 | MyD&D Sword+1 |
|---|---|---|---|---|---|
| No Armour | 60% | 58% | 60% | 72% | 80% |
| Shield Only | 50% | 42% | 55% | 58% | 75% |
| Leather/Padded | 45% | 42% | 50% | 58% | 70% |
| Leather&Shield | 49% | 28% | 45% | 42% | 64% |
| Chainmail | 35% | 42% | 40% | 58% | 58% |
| Chainmail&Shield | 30% | 42% | 35% | 58% | 51% |
| Plate | 20% | 58% | 25% | 72% | 44% |
| Plate&Shield | 10% | 42% | 15% | 58% | 36% |
Grade D (+2) weapons have always had a +1 bonus in MyD&D and so are the same as Grade E weapons under these revised rules. There are two types of Grade D weapons - weapons with a special magical ability and bane weapons.Having these abilities do not make the magic sword more effective as a sword.
- Bane weapons are those listed in OD&D as +1/+3 vs a specific target. In MyD&D these do double damage against the indicated target type (roll double the damage die rather than multiplying by 2). Remember in OD&D all weapons originally did d6 damage, so doubling the damage has the same general effect.
- Magical weapons have special abilities culled from the intelligence powers table. Although I used a modified version of the table by John T Sapienza Jr from Different Worlds 4 so the special abilities are much more varied than the ones fornd in the OD&D table. These powers may be active (which need to be invoked by the user), or passive (and simply affect the user).
Grade C (+3) weapons are reforged in an elemental forge and imbued with the elemental energies of the forge. Mythically they are considered twice-forged weapons as a result. Note that elemental energies include both classical elements such as fire, earth, metal, ice, and stone, but also more abstract elements such as death, undeath, holy, unholy, and even things like love (although a sword or knife embued with love energies is probably going to cut emotional bonds as a result, rather than create them; arrows and clubs on the other hand...). The advantage in these swords is entirely due to their elemental affinities rather than their being better swords, so I don't think I will pursue my original plan of rolling three d20 for a hit roll.
Grade A and B (+4 and +5) weapons are elemental weapons that are forged for a third time, which shapes the elemental energies into a dedicated function. For example am elemental metal sword (a Grade C weapon) can cut through most substances and lesser metals with ease, negating the effects of armour (for example). An elemental metal sword reforged into a sword of sharpness (a Grade B weapon) can cause crippling injuriies with a successful strike. The one-and-only vorpal sword (a Grade A sword) can do the same to creatures that are normally resistant to such injuries. Again, having these powers does not make the weapon a better sword, just a more dangerous one. So again, the hit probability need not be changed as a result.
The corollary of this is, of course, that wearing "magic armour" (Grade E or better armour) causes anyone targetting the wearer to roll two d20 and use the lower result (the same as disadvantage in 5E). Which is a pretty severe penalty. Fortunately, when wielding a magic sword against a target in magic armour both factors will cancel out and a single d20 is rolled to determine the success of the attack. Of course the nature of the other abilities of weapon and armour will affect the fight.
I will point out that high grade magic items are pretty rare, even though I actually have written guidelines of how to forge them. The first step is to find a craftsman with sufficient abilities to make them and convince them (and most likely their employer) to do the work for you. Then there are the materials required, which tend to be rather expensive. And for equipment of grade C and above you will need to find an appropriate elemental node to charge the elemental forge with the required energies. The vast majority of magic items are of the Fourth Rank or less.
