Spell interruption rules in AD&D (and evasion/pursuit rules)

I am wondering if anyone has made sense of Gygax's spell interruption rules in the DMG - perhaps [MENTION=3586]MerricB[/MENTION]?

There seem to be multiple rules, and I don't think they fit together especially clearly:

* Players of spell casters must declare their spells before initiative is rolled (p 65) - I infer from this that you are locked in once the dice are rolled, and that if you lose initiative and then are hit by an attacker who won initiative your spell will be interrupted.

* Page 67 states a rule that allows a chance to interrupt a caster who won initiative, namely, if the absolute value of (weapon speed factor - losing initiative die roll) is less than the spell's casting time in segments (if it equal to the casting time in segments, then the spell is cast and the to hit roll made simultaneously).

* Page 67 also states a rule that says if initiative is simultaneous, the weapon strikes on its unmodified speed factor. This seems bizarre - the prospects of interrupting are actually better if you lose initiative (and hence get to reduce your WSF by your initiative result) then if you tie on initiative (and hence have to use your unmodified WSF).

* Finally, p 65 states the following, rather obscure, rule:


Some comments on this rule: (1) It seems to contradict the rule on p 67, for determining the segment on which the potentially interrupting attack occurs; (2) It is not clear to me, in light of the example, when the opponent's losing roll would ever be the correct roll to use to determine the segment on which the attack takes place. Is it intended as an alternative rule to that on p 67 for attacks that have no WSF? If so, it seems that such attacks will very often be slower than those made with weapons - because under the p 65 rule the attack occurs on the segment equal to the higher die roll, whereas under the p 67 rule the attack occurs on the segment equal to the difference between the WSF and the lower die roll.

Any thoughts or clarifications would be appreciated!

They are hilariously incompatible. I suspect that Gygax rarely used a consistent system for initiative, or perhaps he used a simple system and then created this system for the DMG.

If you haven't seen it, have a look at ADDICT, which constructs a system based on the AD&D Initiative rules that actually works... but it does so by ignoring some of the rules in this section.

I wrote a blog entry on AD&D initiative a couple of months ago.

As to your points:

* Players of spell casters must declare their spells before initiative is rolled (p 65) - I infer from this that you are locked in once the dice are rolled, and that if you lose initiative and then are hit by an attacker who won initiative your spell will be interrupted.

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Absolutely. Declaring spell-casting before initiative has always been part of my AD&D games. Indeed, I have always played all players declare actions, then initiative is rolled, then actions are resolved in the order that makes sense. This may, in fact, be how Gary ran it. "What makes sense" doesn't always work as a system you can write down, though!

Page 67 is just weird. There are some bizarre results that can occur. "Absolute value"? Huh?

(Just removed the example as I'm not sure that it's correct...)
Cheers!

And to think, AD&D was his second attempt to write a coherent combat system....

Scrivener of Doom said:

And to think, AD&D was his second attempt to write a coherent combat system....

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The biggest problem AD&D has is that it was, at no point during its writing, a complete system. Both the Monster Manual and Player's Handbook get away with a lot because Gygax isn't trying to explain how the rules actually work. There are hints, but the actual systems are meant on the DMG. Which then doesn't actually give most of the systems in a coherent form.

This is, in fact, the way that Gygax developed D&D. Every single one of his rulebooks relies on what has come before. To fully appreciate AD&D, you need to know how OD&D worked. To understand OD&D, you need to understand Chainmail. And to understand Chainmail, you need to understand the rules surrounding miniature gaming at the time.

(That said, Chainmail may be the most coherent of the rules. Possibly).

It wasn't until Tom Moldvay came along that we got someone working on D&D who could actually write a coherent rules system! (I wonder what the so-called Rules Editors at the time were doing... especially with the DMG).

Cheers!

Reading through OD&D (via the recent reprint), I got the feeling that the books were written as a reference for those already "in the know" and that the target audience was, for the most part, Gary's extended gaming club and those participating in convention play at the time. AD&D seemed to continue with this sort of tone, written not as a complete game but as a reference and resource for those already playing with some rules simply assumed to have been learned by playing and thus not needing to be written down.

This is my assumption, anyway, from reading through it for the first time 40 years after it was originally published.

MasqueradingVampire said:

Reading through OD&D (via the recent reprint), I got the feeling that the books were written as a reference for those already "in the know" and that the target audience was, for the most part, Gary's extended gaming club and those participating in convention play at the time. AD&D seemed to continue with this sort of tone, written not as a complete game but as a reference and resource for those already playing with some rules simply assumed to have been learned by playing and thus not needing to be written down.

This is my assumption, anyway, from reading through it for the first time 40 years after it was originally published.

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That's also my impression. I don't think Gary made the leap he needed with AD&D to realising it was now a wider audience - and it probably wasn't helped by other business matters taking too much of his attention. The DMG needed a lot more work than it got.

Cheers!

We played AD&D for years - most of a decade. Our games diverged greatly from the published rules. Trying to figure out how to play just from the published materials now completely eludes me.

PS

I came to AD&D from Moldvay/Cook/Marsh B/X.

We changed some rules to fit the new system - AC 10 rather than 9, minute rounds rather than 10 second rounds, etc - but I don't think we seriously revisited the initiative or targeting rules. Though we did use the "segments of surprise" rule, but I think not with all the permutations.

And on the topic of surprise - I think ADDICT gets at least one part of the surprise rules wrong. It has each surprise segment treated as 3 rounds for purposes of missile fire, but I don't think that's what's intended. I think Gygax intends that, in surprise segments, the missile rate of fire is three times what it normally is - so you can hurl one dart per segment, one dagger (or shoot one arrow) every two segments, etc.

The "reason" that melee attacks get to be 10x faster is because in a surprise segment the other side is not defending itself, and so each d20 roll really correlates to roughly one swing, rather than to the luckiest of a series of manoeuvres over the course of a minute of melee.

And on a different topic - I had a look at the pursuit rules today. They're quite interesting, but once again suffer badly from poor editing. The rules for the opportunity to avoid an encounter are split between p 49 (encounter distance and evasion in wilderness encounters) and p 63. And the rules for likelihood of pursuit are split between pp 63 and 67-68. Finally, the rules for outdoor evasion talk about evasion failing and confrontation resulting on "any result of 0% or less" in the context of a d% roll which cannot be less than 01 (because the modifiers adjust the percentage chance of success, not the roll). I think the best interpretation of what is intended here is "if the roll fails by more than 20" - much like the Pick Pocketing rules.

Once these infelicities are cleaned up and the system looked at as a whole, though, it is quite interesting. In many ways it is as structured as a 4e skill challenge, although the mechanical framing of the structure, and the inputs into the resolution, are a bit different.

Does anyone have memories of resolving evasion in AD&D? How did it work out?

I use a mostly by the book initiative system.

Declare actions
Roll initiative.
Winning side goes in order: Movement, Missile/Spell,Melee
Losing side goes in order: Movement, Missile/Spell, Melee
Opposed actions add casting time and weapon speed to the initiative roll.
Spellcasting starts on the segment shown on the die, if you're hit before then, you do not lose the spell. If you're hit during the actual casting time of the spell, you lose it. I.E., Gandalf rolls a 4 for initiative, he has to get hit between segments 5 and 7 to interrupt the spell. Also, if Gandalf had been casting a spell with a casting time of 6 or greater, it won't go off until the next round, a fact people seldom mention when discussing 1e casters as overpowered.

pemerton said:

And on the topic of surprise - I think ADDICT gets at least one part of the surprise rules wrong. It has each surprise segment treated as 3 rounds for purposes of missile fire, but I don't think that's what's intended. I think Gygax intends that, in surprise segments, the missile rate of fire is three times what it normally is - so you can hurl one dart per segment, one dagger (or shoot one arrow) every two segments, etc.

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That's a rather controversial topic. I remember the very long debates that we had on Dragonsfoot. The rules in the DMG could be easily read either way. In one Q&A thread, Gary more or less stated that the ADDICT interpretation is correct, but he suggested to dump the rule. On this I wholeheartedly agree. Even assuming that the rule was originally meant in that way, the tripled ROF per segment is completely out of whack.