Demon Idol

A gamist Advanced Dungeons & Dragons interpretation.

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AD&D combat – especially initiative – is infamous for being open to numerous interpretations, and is often subject to many houserules. Demon Idol provides a defined combat procedure, and this page provides additional rules info.

Points to remember

  • AD&D combat is meant to be abstract. This is not a simulationist game system. There will be times you may think, “That doesn't make sense!” Just roll with it.
  • This is a game, not a simulation. The abstract nature of AD&D combat enables those 200 vs 200 battles of mixed troops, spells, PCs, and NPCs.
  • It is only by keeping a defined combat procedure that players will be able to judge their options and make meaningful decisions. When rules are overridden by DM fiat, the game is typically weakened.

Repeating 20s

We do not use the alternate system on DMG 82. Plusses to attack rolls each bump the result up by one row as normal.

For example, if the opponent's armor class is so high that the final repeating 20 is indicated as the target number (the one just before the target number becomes 21), a +3 strength bonus and a +3 magic sword (total bonus +6) would bring the target number 6 steps down, landing exactly on 19.

Note that a target is effectively unhittable by to-hit roll if the target number is 21 or higher, since the highest number that can be rolled on a d20 is 20.


Surprise bonuses

Being unseen by an enemy party due to an ability (invisibility, psionic invis, hide in shadows) grants +1-in-6 to surprise. Being unhearable due to an ability (silence spell, move silently, psionic invis) gives a separate +1-in-6 to surprise which stacks with any bonus for being unseen. Multiple bonuses for the same sense do not stack (e.g. invis does not stack with hide in shadows).

Blocking off areas and pushing past

To get past an area or portal being blocked off by enemy combatants, combat options are (1) overbear attack as per DMG 73, (2) defeat them in combat, (3) make them fail morale.

Closing to striking range

Combatants who are closing to striking range as their action are not possible melee targets for combatants in the melee they are closing in on, just as the closer themselves cannot attack this round. Furthermore, they are not possible targets when firing into the melee the combatant is closing in on; they become possible targets at the start of the next round.


See Charging.

Repositioning while engaged

A combatant in melee can reposition themselves up to 1“ without breaking off from melee. The shifting combatant can still can make their their regular attacks. Any other movement will require avoiding or magic.

Reaction and initiative bonuses

These are the bonuses from DEX to both (1) shoot earlier or later than the initiative roll, and (2) reduce individual surprise state. In order to receive these bonuses, the following three cases must all be true, as per PHB 101-102:

  1. Max MV. (12” for all standard characters except barbarians and monks.)
  2. Non-bulky armor. (Note that magic armor bumps the bulkiness one category less bulky.)
  3. No encumbrance. (Note that magic armor has half encumbrance when worn.)

Move and shoot

Ranged weapons can be fired at ½ RoF (rounded down) during a turn where ½ MV or less is used.1) Only elves can move, shoot, and move again in one round using this rule, as per the MM (and their total MV for the round is still halved). For non-elves, shooting ends all movement for the round. In the case of weapons which can be fired from a mount, the MV in question will be the mount’s MV.

Grenade-like missiles

If you don't use precise miniatures, exact positioning will not be part of your combat. Therefore, to calculate who is in splash range, some DM fiat needs to be applied. The DM should always be clear with the player about their chances to splash enemies or an ally.

If you're a DM, one great method is to provide the player with two options: (A) splash a lot of people, but that includes some allies, or (B) splash few creatures, but a small or zero chance to splash an ally. Select dice rolls that generate odds that make sense for the melee, always taking creature size into account in the same way you do when determining missile targeting.

When the situation is unclear, the DM should always favor the defenders, whether that's the PCs or their enemies.

Flank and rear attacks

Flank and rear attacks will be determined by “filling up” squares/hexes as per the system on DMG 69-70 in order of “most favorable to defender” to “least favorable to defender.”2) 3) Exceptions will be made when positioning is obvious, such as in a 3’ tunnel.TODO: Expand on how to do this

Mounts attacking

All war mounts and monster mounts get their attack routines beginning on the round following the round they are considered to be in melee.4) Mounts not meant for combat will only fight as a last resort, and will always choose to flee instead if possible.

Remember that non-war horses have a 90% chance to flee at the start of any combat, and warhorses have a 10% chance to flee. Dogs do not have a special chance to flee, but have other downsides mentioned on that page.

Unarmed combat

Morale checks

Targeting downed combatants

This is a rules extension and not mentioned anywhere in the books.Ex

If a combatant is targeted by multiple attack routines in a round, even though attacks may be rolled simultaneously for gameplay speed, damage is rolled one attack at a time. If a character is dropped to 0 HP or lower after a damage roll, the rest of the attacks will likely be re-rolled against different targets if another target is available. The DM may rule that the monster simply continues to maul the unconscious corpse, drag it away, start eating it, etc. But this would only happen with certain monster types such as:

  • Monsters who would reasonably choose to drag a single defeated enemy away and leave the combat (exposing themselves to attacks from avoiding)
  • ntelligent enemies who have a good reason for making sure the dropped enemy is totally dead instead of attacking another enemy.
  • Monsters that are unable to attack another target for some reason. For example, a group of 50 giant rats being too numerous to all attack a group of 4 PCs. (See Targeting.)

If the DM is unsure which option the monster would choose, a 50-50 chance is diced, similar to the dragon breath rule.

We call this the “Tunnel Snakes” rule.

Negative HP

These rules on DMG 82 can be tricky to parse. What they're saying is that a creature can be brought from positive HP to 0, -1, -2, or -3 HP in a single hit and not die. Instead, the creature falls unconscious and begins losing 1 HP per round. However, if the creature reaches -4 or lower HP by any means other than the 1 HP loss per round, the creature instantly dies.

As for binding wounds, we simply consider this a full-round combat action (action type E in the combat procedure). There is no need to manage bandages and the like; any character can stop the HP loss by spending a round tending the downed creature.

It is not recommended to cause any mechanical disability on a character for reaching -6 or lower HP.5) The player may describe a permanent scar of some kind though, and record it on their character sheet as a trophy.

Rounding damage

When rounding damage, such as due to a skeleton's resistance or a save vs breath, always round up.6)

Flying combat

Diagonal movement

Extrapolated from Chainmail.
DMG 70, “…6 would attack frontally, 4 from flank positions, and 2 from the rear.”
We recommend using the two grids which include two “front flank” spots, rather than the “(rear) flank” spots. This will typically result in mostly front attacks, a couple shieldless attacks, and a couple rear attacks. At least, for medium-size-creature vs. medium-size-creature combat. Extrapolate for size differences. Aim for a “slot” ratio of 3:2:3 front:flank:rear. If you use rear flank spots instead of front flank spots, the defender will get hit much more, since rear flank attacks don't allow shields or DEX.
MM 53 lists this for warhorses, and we extrapolate it for other mounts.
As stated elsewhere in the book, such wounds are not the stuff of the genre fantasy.
MM 51, “Hell Hound” sets the precedent. Also, doing at least 1 HP of damage makes sense.
combat.txt · Last modified: 2024-02-20 00:52 by