Blast from the Past: Counterspelling in AD&D!

I love a spell duel. The scene from Conan the Barbarian movie where the two mages go at it... pure gold!

When I read a post by a gent named duBeers from the wonderful OD&D Boards forum that covered how he did counterspelling, I had to go write my own. After all, if Chainmail could have counterspells, then the game that it influenced, Dungeons & Dragons, could have it too.

I've been using these for the past nine years. When it's happened in-game, it's been pretty intense to see the players get into it. It shocks the crap out of the mages every time I do it, because they forget that it's an option. My monsters and NPCs don't forget...

Here's how it works:

A magic-user may use his or her arcane knowledge to attempt to neutralize an opponent's spell. This is referred to a counter-spell or spell duel.

1. To engage in a duel a magic-user must be able to see the attacking magic-user.
2. Any condition which would prevent a magic-user from casting a spell would likewise prevent him or her from countering of a spell.
3. Cleric spells cannot be countered.
4. The intent to counter a spell must be declared during round declarations. The DM will let the players know if a monster is casting a spell.
5.  Attempting a counter-spell fully occupies a magician's powers and concentration. Engaging in a counter-spell duel negates any further action or spell use by both participants for the remainder of that round.
6.  The spell duel resolution occurs in the Phase/segment that the spell would have finished in.

Resolving a Spell Duel

1. Compare the levels of the countering magic-users with the spell-casting magic-user.
2. The mage casting the spell performs a saving throw vs. (Unlisted) Spells. They add (or subtract) the difference of level (HD) between caster and counter-speller. If the save is successful, the caster wins the duel; if not, the counter-speller wins.
3. The loser of the spell duel must roll against the table below: 

2d6 Result (+1 for each 2 levels that casting MU's level is higher than countering MU)

2	Unconscious 1d4+1 rounds
3	1d4-1 points damage
4-5	Confusion (1d4+1 rounds)
6	Charmed - under control of winner of the duel
7-9	Suffer effects related to attempted spell*
10	Forget one spell (randomly chosen by DM)
11	Forget all spells
12+	Feeblemind (equivalent of 3 INT until a full day’s rest, all spells forgotten)

* to be determined by referee

Example: Treen, a 2nd level mage, sees that a goblin shaman is about to cast a spell and declares that he will counter the shaman’s spell. The goblin is an HD 1-1 (considered a 1) so must add 1 to their roll. The goblin must roll a 12+1 = 13 to save against Treen’s counter spell. The goblin rolls a 3. It then rolls a 6 on 2d6 and is now considered charmed by Treen.

(Image credits: A duel between wizards in Alphatia is always to the death. [Stephen Fabian, Gazetteer: Dawn of the Emperors by Aaron Allston, TSR, 1989])