Dispell Magic: Unless countered, this spell will be effective in dispelling enchantments of most kinds (referee's option), except those on magical items and the like. This is modified by the following formula. The success of a Dispell Magic spell is a ratio of the dispeller over the original spell caster, so if a 5th level Magic-User attempts to dispell the spell of a 10th level Magic-User there is a 50% chance of success. Duration: 1 turn. Range: 12".Dispel Magic is, conceptually, an instantaneous effect, although the 1 turn duration may be necessary to cover temporary suspensions of effects from magic items, since a magic item is not permanently affected by Dispel Magic. The range could fit into Line of Sight easily.
There is no explicit limit mentioned, but since the spell description doesn't mention an area of effect, I'll assume Dispel Magic only targets one object or creature which has been enchanted, but perhaps multiple enchantments simultaneously.
There's an "Unless countered" reference at the beginning of the spell description. This may be a fleeting reference to the Chainmail idea of counterspelling, which some OSR bloggers have attempted to work back into OD&D. On the other hand, maybe "countering a spell" doesn't mean anything more than standard distraction techniques, which could be handled magically with an illusion or Light spell, or physically with a thrown rock. Either way, there's no need to use Dispel Magic to disrupt spells in the middle of casting, so we can limit it to enchantments already cast.
Dispel Magic is not automatic unless the level of the caster is equal to or greater than the enchanter's level. In later editions, lower-level users of Dispel Magic have a 5% penalty per level, but here in the original rules, it's an actual ratio. I'm thinking I might prefer the original rules, but with quite a bit of rounding so that I can stick to using a d6. Something like:
- If you try to dispel an enchantment placed by a higher-level caster, you fail on a 5+ on 1d6.
- If the enchanter is only 1 level higher, you get a -1 on this roll.
- Otherwise, You get a +1 if the enchanter is twice your level, +2 if 3 times your level, and so on.
- Wizard: low-level M-Us get +1 to failure chance
- More Than Wizard (powerful demons, for example): standard failure chance for Wizard, +1 for Sorcerer, +2 lower levels
- Godling: add an additional +1 difficulty