Very little. But it's not quite as you say. The loser in the comparison of pools loses dice from their pool (if monsters), or from their CON (if PCs), and so there is a death spiral effect for monsters but not PCs. (I'm simplifying the monster side of things a little bit: the pool reduction is mediated via a reduction in "monster rating" which is what sets a monster's pool.)
Monsters have a monster rating. It's their HP, and it determines the base dice and base adds of the monster. (dice = MR/10, min 1; adds = Current MR/2.) Ken has waivered over the years between "dice don't change, only adds" and "damage reduces dice"... the later ups calculation times. 5th makes neither dropping a legit option.
PCs get dice by weapon, adds by attributes.
High side does damage to low-side equalling the difference in combat totals. (Note, melee has no rolls to hit. Just go straight to the damage rolling.)
It seldom results in 1 roll combats.
Spells can require rolls, missiles require to-hits...
Have you ever played an RPG that allowed either GM or PC choice of more than one combat system to use? Warmech games and old(er) Shadowrun may fit this bill, with the machines/matrix getting separate sets of rules. I'm also interested in games that offer two options for the same battle - not depending on whether you're driving a robot destroyer or driving a laptop/neural implants.
Which combat system did/would you prefer? Did you start a battle and wish you had used the other rules? Did you finish a battle and regret or savor the choice of rules that you made?
It occurs to me because I used to dismiss the possibility of using my game's base rules (first two modules) for combat, and assumed that two additional rules modules were necessary for real combat. I recently realized that the base rules present a significant alternative to the crunchier combat set, summarized as:
Simple combat: mainly using die contests (PC vs. GM d20s) and character skill to determine victory in a combat, no structure for taking turns, and emphasis on narration.
Extended combat: emphasizing damage and protection, structure in timing and quantity of effort (initiative and actions), with emphasis on tactical choices.
TL/DR: think Dragon's Lair versus Warcraft. Gory details:
In Modos RPG, the first two rules modules (core and character) provide for outcome-deciding contests with bonuses from attributes and skills. A series of these can be considered a simple conflict - a sort of story-telling-type of battle. Side rules play into these. GMs are encouraged to give 2-point bonuses for good descriptions from PCs. Without a rule resembling health or hit points, PCs instead add to their character Flaws ("lost kneecap" or whatever the case may be). Shields are an important consideration in simple conflict because they add to a character's parrying (blocking) skill. But parrying requires an action in...
Extended conflict ties in its own module and a combat module to form the more traditional type of battle. PCs lose health when they take damage and take less damage when they wear armor. They take actions, turns, and sometimes jockey to gain the initiative. Parrying plays a side role because it costs an action, but armor always provides protection, which is important because an unparried attack almost always does damage. Goals and Flaws can contribute because they can still provide d6 bonuses ("hero points"), but flaws are not needed to track damage. Positioning takes place in zones, but is otherwise as flexible as the free-form simple conflict.
I guess this is not what you're looking for, but for me D&D itself offers at least two combat systems: TotM and the full default combat system.
In TotM you don't keep much track of positions, distances and such. It might vary in the level of approximation: one DM might not bother where things are even in broad strokes as long as you know who is in the battle, another DM may work loosely with near/far conditions, but you very rarely track distances accurately because in TotM you have no visual aids. So the result is to use a somewhat incomplete set of rules compared to the full default system.
I know many DMs who use TotM for short, unimportant battles and the full system for featured encounters. Personally I even occasionally skipped the combat rules completely and reduce trivial encounters to a couple of rolls, making something up in terms of random possible costs for the PCs. Even if you just decide not to use HP for smaller monsters and let them die at the first hit, in a sense you're using an alternative combat system.
That seems more like "one combat system with optional elements." It can be a very useful way to run things. In the session I played last night, the main fight was run this way, because it was a 1:1 duel, and there wasn't any need for a map.
I have played a couple of games with two combat systems. One was a homebrew WWII game that used Advanced Squad Leader for small-unit combat and its own system (designed to interface to ASL) for close-up confrontations.
The other came out of the DM's own system, which is intended to be a more detailed form of D&D and is complicated. We were playing AD&D1e, and a very consequential duel needed to be staged, because of dishonourable conduct by a PC in a pseudo-Japanese society. The DM wanted to run it under his combat system, but I declined because I wasn't familiar with it, and it was looking really complicated.
Monsters have a monster rating. It's their HP, and it determines the base dice and base adds of the monster. (dice = MR/10, min 1; adds = Current MR/2.) Ken has waivered over the years between "dice don't change, only adds" and "damage reduces dice"... the later ups calculation times. 5th makes neither dropping a legit option.
PCs get dice by weapon, adds by attributes.
High side does damage to low-side equalling the difference in combat totals. (Note, melee has no rolls to hit. Just go straight to the damage rolling.)
It seldom results in 1 roll combats.
Spells can require rolls, missiles require to-hits...
And damage gets distributed to PCs in a very hit-point-attrition model. It is a simpler tactical combat system, but probably not what Niklinna wanted it to be.
That seems more like "one combat system with optional elements." It can be a very useful way to run things. In the session I played last night, the main fight was run this way, because it was a 1:1 duel, and there wasn't any need for a map.
I have played a couple of games with two combat systems. One was a homebrew WWII game that used Advanced Squad Leader for small-unit combat and its own system (designed to interface to ASL) for close-up confrontations.
The other came out of the DM's own system, which is intended to be a more detailed form of D&D and is complicated. We were playing AD&D1e, and a very consequential duel needed to be staged, because of dishonourable conduct by a PC in a pseudo-Japanese society. The DM wanted to run it under his combat system, but I declined because I wasn't familiar with it, and it was looking really complicated.
AD&D (and D&D as a whole, over it's lifetime) has had a lot of stuff like that. At the basic level, regular combat with the side option of spells fits the model. As does situational combat (naval, flying, maybe even ranged/reach/mounted) using the same basic to-hit/AC/hp/damage system if the specifics overshadow the base mechanisms (turning radius on fliers swamping attacks/round in terms of determining who gets more attacks on who being an example). Throw in Psionic combat or 3e mage duel (from Magic of Faerûn) or 1E Oriental Adventure's psychic duel (an intimidation/nerve staredown, not psionics) or Battlesystem and there's lots of ways you can defeat each other (just not where you choose which system, except by showing up with a psionic, dragon-rider, or boat).
In OD&D, combat is resolved using Chainmail by default. (The d20 system being an optional alternative.) Chainmail has three combat systems: the normal mass combat rules, the "man-to-man" rules, and the "fantasy combat" rules. OD&D itself doesn't provide any guidance about which system to use in a given situation, but Chainmail makes the uses for each somewhat clear. I haven't played OD&D, but I have run a few small battles using the mass combat rules from Chainmail.
The "man-to-man" rules state they're for small skirmishes, seiges, and the like. They're only good for fights between humanoid opponents, and I think I would only use them for exchanges involving two combatants, so in a duel for example, although ranged weaponry can also be used in this system.
The "fantasy combat" system is for fights between certain types of monsters and characters and is a kind of class feature, coming online at certain levels, so I could see it being invoked on the player as well as the DM side.
I'd use mass combat for everything else as much as possible.
Cortex Prime has multiple ways to resolve conflicts.
Tests - You roll against the difficulty they rolled, you win, and they're taken out.
Contests - Each character rolls to beat the number rolled by the other until one side fails to beat it and is taken out or one side gives in.
Action Order Resolution - Typical round-by-round kind of deal.
Challenge Pools - The obstacle or opposition is represented as a dice pool. The PCs take turns trying to knock dice out of the pool, suffering stress when they fail. Each "round" the challenge can "attack" a PC.
Crisis Pools - Kind of like a challenge pool, this represents some impending crisis. The biggest difference is it can grow.
A Cortex Prime game can use one or multiple methods (Tales of Xadia uses tests, contests, and challenges).
In OD&D, combat is resolved using Chainmail by default. (The d20 system being an optional alternative.) Chainmail has three combat systems: the normal mass combat rules, the "man-to-man" rules, and the "fantasy combat" rules. OD&D itself doesn't provide any guidance about which system to use in a given situation, but Chainmail makes the uses for each somewhat clear. I haven't played OD&D, but I have run a few small battles using the mass combat rules from Chainmail.
The "man-to-man" rules state they're for small skirmishes, seiges, and the like. They're only good for fights between humanoid opponents, and I think I would only use them for exchanges involving two combatants, so in a duel for example, although ranged weaponry can also be used in this system.
The "fantasy combat" system is for fights between certain types of monsters and characters and is a kind of class feature, coming online at certain levels, so I could see it being invoked on the player as well as the DM side.
I'd use mass combat for everything else as much as possible.
Technically, no, players do not. Because Cortex Prime is a construction set, not a game in itself.
The GM determines which are included in the specific flavor they build. A GM can include multiple and allow the choice, but is not, RAW, required to include any of them... because it's not a finished ruleset, but a toolkit the GM is explicitly supposed to subset.
I’d thought about mentioning them, but I don’t see the rules for jousting as a combat system per se. It’s more like having the rules for Three Dragon Ante and other dice games in the DMG. It could be considered a literal example of “combat as sport”, I suppose, but I think in Chainmail, and thus in OD&D, you’ve got three systems for the same sort of purpose and one that’s clearly meant for something else. One of these things is not like the others and all that.
Kind of? The GM normally decides what mix methods are used in a particular game. In my own games, taking down say a doorman at a club or just a solo guard is likely just going to be a test. If you're using contests, the player may choose to initiate one (by saying something along the lines of, "I'm doing this, who's going to stop me?" or choosing whether or not to engage with someone else trying to do something). But the idea is to follow the fiction and what's important.
