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

[pemerton]

Group initiative and order of combat fom B/X was one of my first rule imports

You mean you imported it from B/X into AD&D?

I was skim-reading the Moldvay rules the other day - I didn't find anything on spell interruption. Is it there but I missed it?

 

[ashockney]

We relied heavily on our interpretation of the "other weapon factor determinants" paragraph at the bottom of p66 and top of p67 of the 1e DMG, and this is what we did:

We checked for surprise, if it was won by either side they got to act first (taken from initiative for creatures with multiple attack routines, p62 of the 1e DMG).

We then had everyone declare their actions for the round.

Everyone then rolled initiative, which was a d6, subtracting their Dex Modifier for Reaction adjustment ad adding their Weapon Speed Factor (minus 1 for each +1) or Casting Time in segments. If you had "multiple attacks" as a fighter or monk, you added your Weapon Speed Factor (minus 1 for each +1) again for each attack to determine what segment of initiative your attack occurred. Finally, if your action included movement, you added 1 segment for each 1/10 of your movement (walk, charge, fly speed) to arrive to your target for melee.

For example, nobody is surprised and we are 3" away. A fighter rolls a 5 on initiative (no Dex mod), and wielding a short sword +1 (WSF 3-1=2) and has a 12" move. The fighter is moving to attack a caster. Everyone rolls initiative, and the DM works up from 0, 1, 2, 3, 4, 5). On 5, the fighter begins to move to the caster and will arrive on 8 (1.2" per segment, 3" away). On 8, the fighter arrives, and now adds his WSF of 2, and will complete his attack on segment 10. On 10, I roll to hit, succeed, and do 4 points of damage, which would interrupt if his spell was casting at that time.

The caster's initiative roll on a d6 is a 3, has a +1 Dex Mod, so he begins casting on a 2, and is casting fireball with a CT of 3. On 5 (when the shortsword-wielding fighter action begins), the caster completes casting a fireball - without interruption.

If he had "attacked" anytime in the casting time (segment:2, 3, 4, or 5 (because he would win a tie)) the spell would be disrupted and lost. Also, if he had been in melee and won initiative he could have "held" his attack to disrupt the caster.

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:

"Attacks directed at spell casters will come on that segment of the round shown on the opponent's or on their own side's initiative die, whichever is applicable. (If the spell caster's side won the initiative with a roll of 5, the attack must come then, not on the opponent's losing roll of 4 or less.) Thus, all such attacks will occur on the 1st-6th segments of the round."​

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!

 

[ExploderWizard]

You mean you imported it from B/X into AD&D?

I was skim-reading the Moldvay rules the other day - I didn't find anything on spell interruption. Is it there but I missed it?

Yes. The import was from B/X into AD&D. The B/X is system is streamlined, and smooth. The only alterations required are for those spells that take a full round or longer to cast. B/X doesn't futz about with minute casting time variations.

Spell interruption is on page X11 of the Expert set under casting restrictions.

 

[Libramarian]

I ran AD&D for 6 hours yesterday (the old Dungeon adventure "Falcon's Peak"--a nice SWAT mission-style 'realistic' dungeon). I implemented the change to spellcasting initiative and I like the randomness it adds to spell vs. spell and charge vs. spell. The 1e initiative system is really not too bad. Melee and spell initiative is all fine and I think it adds enough to the game to be worth the complexity. The only part for me that is truly a PITA is dealing with movement in segments, especially when combined with missile range categories.

E.g.
3 hobgoblins are charging an archer from 80' away. How many arrows can they get off in time?
Monsters rolled a 3 initiative and the archer has 16 Dex so -1 modifier.
PC fires at 2 and 5 (I say ROF 2 missile weapons fire 3 segments apart, and ROF 3 fire 2 segments apart)
Hobgoblins have 9" movement, but are charging so 18", which means 18' per segment.
At segment 2 the hobgoblins have moved 18 * 2 = 36'. PCs gets their first shot here.
80' - 36' = 44' away from PC (compare to range categories to determine if there is a penalty. No penalty)
In 5 segments the hobgobs can move 5 * 18 = 90', which is > 80' so the PC can't get their second shot off in time.

This is too much for me in the heat of battle. I'm going to make a movement rate * segments = distance table and see how much that helps.

Unfortunately, page 101 is not a rule. It seems to be a reference to the Eldritch Wizardry initiative system (where armour has an effect on initiative), but the actual effects of the rule are never detailed.

I think it's clear what the effect is meant to be for the first two encumbrance categories (at 12" you get your full Reaction/Initiative bonus, at 9" you lose it) but it's definitely not spelled out what "slowed" and "slowed greatly" mean for the next two categories.

And then have a look at the Example of Melee (DMG page 71) and there are some additional oddities:

Here's what happens:
* Party A surprises party B for 2 segments
* After surprise, Party B win initiative
* Blastum casts shocking grasp to kill Arlanni, despite Arlanni wielding a sword. (In theory, you'd compare casting time vs losing die roll and weapon speed).

It's not mentioned what the initiative rolls were, only that B wins, so this could make sense if A rolled a 1 and Arlanni is using a broadsword or longsword (SF 5).

* Abner casts web and spoils Blastum's next spell, despite it being still round 1 of the combat!

This is truly strange and I have no explanation for it. I don't like the sound of that...so I'm not going to try to find one

Oh, more weirdness with the example of combat in the PHB (page 105):

Surprise goes to the party and the magic-user starts casting a sleep spell (1 segment length), but in the first round of combat the orcs win initiative and spoil the magic-user's spell! Given it should commence during the surprise round, this seems very strange.

I actually like this idea: spells cannot be completed during surprise but if you begin casting during surprise you can skip initiative in the first round (so you complete the spell after the casting time in segments into the first round without referring to the other side's initiative roll). Even though the sleep spell will complete just 1 segment into the round, the other side always gets a chance to interrupt if they win initiative, so the orc could interrupt the spell. This would also solve the problem @pemerton brought up about how to resolve AoE spells during surprise where some targets are no longer surprised.

However it's definitely in conflict with the DMG combat example because Gutboy is hit by Command and Magic Missile while surprised.

Does the rule for multiple attack routines apply to missile attacks?

If so, then an archer always has a chance to interrupt (regardless of DEX) because s/he gets to go first and last in the round.

No, I don't think so. On DMG p 63 under Missile Discharge it mentions using the Item Saving Throw table to determine what happens to an arrow that fires at the same time as the discharge of a fireball spell.

 

[MerricB]

I ran AD&D for 6 hours yesterday (the old Dungeon adventure "Falcon's Peak"--a nice SWAT mission-style 'realistic' dungeon). \\

Seems awesome. My group finished clearing out the Dungeon of the Fire Opal yesterday. I was using an (on-the-fly) AD&D conversion of Jon Tweet's 3e expansion of the original AD&D DMG example dungeon. One of the PCs died of fright when they came up against a ghost. (Aged 10 years, failed System Shock check!)

I'm going to go look at the B/X initiative systems now. Thanks for the page reference, [MENTION=66434]ExploderWizard[/MENTION] - I'll also check if it made it into BECMI!

Cheers!

 

[pemerton]

I say ROF 2 missile weapons fire 3 segments apart, and ROF 3 fire 2 segments apart

Just checking - does this mean that, in your system, a low-DEX character (with a DEX reaction penalty) might miss out on getting all their missile attacks?

(Although in practice, at least for PCs, this will be clerics only barring serious curses or similar, and as best I recall they don't have any high ROF weapons.)

 

[MerricB]

Here's my recounting of how initiative worked in the 1977, 1981 and 1983 versions of Basic D&D

Cheers!

 

[Libramarian]

Seems awesome. My group finished clearing out the Dungeon of the Fire Opal yesterday. I was using an (on-the-fly) AD&D conversion of Jon Tweet's 3e expansion of the original AD&D DMG example dungeon. One of the PCs died of fright when they came up against a ghost. (Aged 10 years, failed System Shock check!)

I'm going to go look at the B/X initiative systems now. Thanks for the page reference, @ExploderWizard - I'll also check if it made it into BECMI!

Cheers!

It was awesome but a meatgrinder--three out of six PCs died. One fell through a trapdoor into a crypt with a wight and was level-drained to 0. He sacrificed himself holding off the wight so the other party member that fell through could escape...after learning that when you're drained to 0 you can never gain xp again.

I like the little oddities of the 1e rules like System Shock and Bend Bars/Lift Gates. One PC made a Bend Bars check to break the lock on a chest without damaging the contents.

Just checking - does this mean that, in your system, a low-DEX character (with a DEX reaction penalty) might miss out on getting all their missile attacks?

(Although in practice, at least for PCs, this will be clerics only barring serious curses or similar, and as best I recall they don't have any high ROF weapons.)

Hmm, no. I don't take the concept of segments seriously enough to have them miss an attack, or delay it to the next round. If that ever came up I would let them get their last attack sometime at the end of the round, after everything else happens. Like how zombies always act last, even after something happening in segment 10.

 

[pemerton]

[MENTION=6688858]Libramarian[/MENTION] - thanks for the reply! What you say makes sense.

 

[MerricB]

I've continued my tour of D&D initiative systems with the 2nd Edition Initiative Systems, or at least three of them - Combat and Tactics will come later.

I found a couple of interesting comments by Steve Winter about the development of 2nd edition initiative that you may find interesting.

Cheers!