These are marked down explicitly mostly so everyone can see why certain rules are in place and the intent behind them. Specific rules and rulings can and will change over time, but the intent will not change.
Balance over Realism is one of the big things I want to highlight. There are rules in place throughout the site that do not make logical sense, because they are not meant to be. In real life, you can die while sitting on a toilet from a sniper a mile away making a shot through your window. That's realistic, and it's very possible in the real world. I have no intention of ever allowing that to happen here, because it's not fun and it's not able to be interacted with. I also firmly believe that 'writing skills stronger' is not a healthy design philosophy because it rewards those who spend time abusing the system and punishes those who play by the rules. A punch that is inhumanly fast here is just that -- inhumanly fast. It does not increase the damage output of that punch, only the speed at which it is thrown. All skills of the same type (in this case speed) need to function the same way mechanically and differ only in flavor for the system to function. Nobody will ever get more than one benefit from a combat ability, ever. Everyone plays by the same rules.
Creativity over Balance is another of these core design decisions that everyone on the site has a right to be aware of and does not invalidate that last point in any way. In any system that allows members to create their own abilities rather than picking from a pre-approved database of such, they will create things that the creators of the system never dreamed of. There will be, quite frankly, some really weird stuff that is presented for grading and I want to encourage that. While a hard stat system with exact numbers is arguably much more balanced, it would come at the cost of stifling creativity and forcing people into very narrow build paths because a mathematically superior option or 'meta' would soon be discovered and exploited. When everyone builds the same things in a progression system, there is only less powerful and more powerful.
Flexibility over Hard Numbers is the third big thing that I believe requires an explanation because I fully anticipate that it will be controversial. At its core, this site is a RWBY AU site. Going beyond the limits of what we think are possible is a core component in any anime, and every character should have the opportunity to go slightly beyond their usual limit if it makes sense. It is reasonable to assume that someone would want to cause more damage to someone who just killed a family member than to someone they happen to be sparring with at the gym, and hard numbers don't give that. 'Limit breaks' and the ability to go slightly beyond normal limits can be character defining moments, like pushing onward for a friend even when the system says that you should be too exhausted to continue. In PvP combat, these 'limit breaks' would have to be agreed upon by both parties to ensure that balance is maintained… but PvP isn't the only form of combat on the site. Most characters are training to be Huntsmen (and women!) whose goal is to defend mankind from the Creatures of Grimm. In a PvE encounter against those Grimm, the flexibility afforded by not having hard numbers allows for character defining moments to happen where against all odds someone does do something better than they normally can because the pressure and need to protect life propels them to those heights.
The design goal of this system is that each character is powerful in their own way. They have their semblance, and they have a set of combat abilities that allow them to be very good at a select few things. There are not enough slots to make your character good at everything, and that is fully and completely intentional. The goal of the system is freeform combat where the player and the combat moderator knows exactly what that character is good at, and it is your goal as the writer to exploit those points of strength as much as possible. A glass cannon in a small room with a tank is going to get pummeled, but a slow melee-focused tank against a ranged speedster will have a hell of a time doing a lot if the environment is an open field. Those that play to their strengths and manipulate the fight to showcase those things will generally win fights even against opponents who have higher ranked skills if that opponent does not do the same. This is considered a feature, not a flaw because clever strategies and good writing should be able to overcome small to even moderate rank differences so that very rarely is the winner of the fight predetermined before it happens.
First of all I want to state that the guidelines below are, as befitting on that 'flexibility over hard numbers' bit in the design philosophy not hard numbers. They may even change over time, though any change to these will be announced and likely part of a larger update post in announcements. I'm going to post the answer as it is now with the design intent of each decision alongside it.
Okay so you have this progression system, but what are the differences in rank and what does that mean for play?
Each tier difference is roughly equivalent to a 33% difference, or 1/3. This is an advantage, but not an overwhelming one. If you are one rank up on someone in speed, and they try to race you… well, they'll lose. In a fight, though, it means that even one tier of difference is not enough to remove the risk of failure. It gives an advantage, sure, and it means that close decisions will likely lean towards the end of the person with the higher skills for the situation. Therein lies how the system is intended to work, though, skills for the situation. Having high ranked speed doesn't mean anything if you're fighting in a confined space where that speed can't be used.
Two ranks is a significant advantage, but it is still possible for that advantage to be overcome if the opponent can think of creative ways to mitigate those advantages. Clever thinking and good writing can trump mechanical advantages, but the road is much more difficult for the challenger in that case. An average first year could win a fight against an average senior year if they got exceptionally lucky or they managed to find a way to mitigate or nullify what the fourth year was good at. It isn't likely, but the chances are above zero and increase if the senior decides to not take the fight seriously at first.
A core thing that is enabled with this is teamwork. Getting friends involved greatly swings the odds, because the differences between ranks are so low. Someone with a full F rank kit will be at a disadvantage against someone with a full E rank kit… but if you put two trainees with full F rank kits against that person with an E rank kit -- suddenly the E ranker is at a significant disadvantage. Forum RP is inherently a collaborative enterprise, and at the end of the day the design goal is for a lot of things to be team efforts. The concept of a lone badass outnumbered and still kicking ass is a fantasy, but not one I care to support very much on a forum based on a fandom that emphasizes the importance of working together as a team.
Three ranks of difference is at the point where the chances of the other party winning are actually zero. The system is designed so that this scenario will never realistically happen in terms of full kits, but it may very well happen in PvE or in single abilities once the site has been around for longer. At three ranks of difference, numbers cease to matter and you basically steamroll the lower power Grimm like the Elite Huntsman you would be at that point.
How much wiggle room is there within skills for creative usage?
The answer depends on whether it's PvP or PvE. Top-down, this system is designed so people have a limited number of tools in their kit to use that everyone is aware of OOC so that nobody is blindsided by random new powers perfect for the situation like Superman. For example, you could have a speed skill that allows you to run fast or a leap skill that allows you to clear the same distance at the same speed but have a different flavor and potential uses. Speed is useful in all circumstances basically, but leap shines more in fringe cases. It's a physical enhancement. Leap is an ability, which generally sacrifices versatility for situational strength.
For example, a rooftop chase. A speed skill would be able to zoom from one end to the other of a roof, but without an acrobatics/parkour skill the actual jumping and rolling would be hard. Not the case for leap! Landing is part of the skill, so you could frog hop all across town with it until you got tired!
You can also use other people's semblances against them. For example, if Johnny Strongman and Flamebob Dinglepants have a fight and Johnny's semblance is a Physical Boost that lets him punch really hard and knock people back with the concussive force of the punch and Flamebob's semblance was Flame manipulation and creation, there are a number of ways this battle could go down. Flamebob decided to set, say, a cart full of oil on fire. It's now burning, and Johnny decides he was to punch either the cart or the oil at the top and use the punch's knockback ability to fling the burning oil onto Flamebob. Either thing is allowed, and a creative use of a semblance.
You said it depended on PvE or PvP, though?
I did! But the answer was getting too long so I split it up. In PvP, there's an expectation of a level playing field where everyone is playing by the same rules. The system falls apart if one person gets OP stuff and another doesn't. We all have the same number of skill slots that we can upgrade through using XP. In PvP rules can be bent if both parties agree, but in stuff like tournaments and moderated combat they will be enforced heavily to ensure fairness.
PvE, though? Grimm don't get to complain about PCs being OP and have no expectations of fairness. Player Characters can carry a backpack full of Lightning Dust with them to fight, and Grimm can't. That's an imbalance, but it's one I'm willing to have in order to let people have cool anime moments in PvE. In PvE situations, rules will not be enforced as long as you don't go too crazy with it. You're not doing an A rank attack with an E rank semblance, for example, but identifying a weak point and doing a critical hit is A-OK even if that wouldn't be allowed in PvP because calling critical hits on another player is... unfair. Grimm don't get fairness, sorry for any Grimm who might be reading this.
So if stamina is a combat ability, how long can a character normally fight for?
The general rule here is four posts of going all out and defending/attacking each turn at the untrained rank with each subsequent rank increasing that number by one. This one is more loosey-goosey than other rules, because it's much more case-by-case than hard and fast ruling. There is a huge difference in energy expended, for example, in Pyrrha throwing her shield out and returning it like Captain America and forcing an entire elevator to go several stories upward with her magnetic semblance.
The design intent here is for fights to not last for literal weeks/months out of character and for each round to feel like it means something. I'd rather have four hype action-filled post cycles rather than a longer fight with stretches of nothing significant happening.
Okay so durability is another combat ability, so how does that work?
Durability makes your character take less damage from enemy attacks. For the purposes of TRP, any ability that you take that gives you durability unless otherwise specified is flavor-wise a representation of how much damage your character's aura blocks. More durability means your aura is more efficient is blocking attacks.
For a general guideline, let's make a mental picture of a health bar based off of percentages. You start with 100%. A G rank punch that directly lands against G rank durability might turn that 100% into 67%. A D rank punch, being 3 ranks higher than G rank would be enough to turn that 100% into 0% due to the three rank difference and each rank being approximately 33% stronger than the last. Glancing blows should do less, and the previous example was assuming a direct hit of full force. In less than three ranks of difference, you can assume that your character's aura protects them from harm or any physical injury until it runs out. Continuing to fight when aura is depleted means that character injury is on the table, however, and should only really be done in Death Enabled threads.
So the whole martial arts/marksmanship/strength/weapon thing, how does it work?
Every character on the site starts with an F ranked weapon. This weapon can and usually will have a melee and ranged mode, but does not have to. The mechanical bonus that these weapons have is damage, plain and simple.
What weapon rank does not do, however, is automatically make a character good at using it. Martial arts is a generic term for a combat ability focusing on melee combat, and marksmanship is a generic term for a combat ability focusing on ranged combat. Martial arts makes you more accurate and more able to justify dodges and deflections. Marksmanship increases the effective ranges for ranged weapons by making you more accurate and able to track moving targets.
Taking marksmanship means you're good at aiming with just about anything. Frisbees, guns, bows... whatever your character could have reasonably used in the past. Same goes for melee, you're be good with unarmed, swords, spears, etc. and basically everything not considered an 'exotic' weapon. What counts as exotic? Weird stuff. Gunchucks, scythes, claw weapons, and giant laser cannons would all count as 'exotic'.
Neither martial arts nor weapon skills allow one to big up giant rocks and throw them at people, though, and strength lets characters do just that. Damage is either done by semblance rank if that is used for damage, dust rank if that is used for damage, weapon rank if that is used for damage, or strength if none of the first three are used for damage. Leveling strength allows your character to both be strong as hell and allow them to do damage in the process at a level equal with the rank of that strength.
How does Speed and Range interact?
Assuming two characters of equal rank face off, it will take the speedster about a second to close the gap into melee if they go in a straight line. Going in a straight line, though, means they'll eat one full attack from their enemy to close in that quickly. If the speedster doesn't go in a straight line, you freeform it out a lot more but that's a guideline that is set down to give both roleplayers something to work with.
Okay, so what’s the difference between Agility and Acrobatics?
Agility is basically your ability to avoid damage. It’s the counterpart to the Durability skill insofar as its main function is to reduce the damage coming your way. While Durability accomplishes this by reducing the amount of damage that you take when you are hit, Agility is used to dodge hits and reduce/avoid damage on falls and throws. Acrobatics on the other hand, which could also be called parkour or wall-running or pole vaulting or anything else is your mobility. Speed let’s you go in a straight line, but acrobatics lets you go laterally and up and down. This is your wall running and your leaping from rooftop to rooftop type stuff. Acrobatics does not reduce damage taken and is entirely a mobility skill similar to flight that opens up different options both in and outside of combat.
How strictly will this system be enforced in play?
It depends very much on what type of thread it is. If it's PvP, if both sides agree the system can be fudged. If it's a PvP event like a tournament, the combat system will be adhered to in order to ensure fairness on all sides. Basically, any sort of PvP interaction has the baseline being 'following the combat system to a tee' with both participants having the ability to decline the use of a battle moderator if they both want to predetermine a fight OOC before writing it out.
In PvE, though, enforcement will be much more lax. The restrictions on Dust usage to balance PvP are lifted for PvE encounters, so much more will be allowed. Grimm don't get the same right to a level playing field that players do, so freeform it up.
The following table measures the DAMAGE done to AURA in ONE ATTACK (which is noted to be a mechanical attack. 10 lightning fast sword swings is the same as 1 measured one, and 10 speed arrows fired is the same as 1 carefully aimed one) when comparing WEAPON/STRENGTH/SEMBLANCE rank (whichever is most applicable) against DURABILITY:
Note: Attacking with a DAMAGE skill 3 ranks higher than the defending DURABILITY skill will result in an IMMEDIATE AURA BREAK. Similarly, defending with a DURABILITY skill 3 ranks higher than a DAMAGE skill will result in damage only equal to one percent of the opponent’s aura.
Additional note: The Clock Rule states that while multiple attacks can be done in a post, each must use the damage value of a different ability and must have an accuracy use that makes sense. The accuracy skill can be the same for multiple attacks, but each instance of damage must be its own separate skill.
For instance, you can use your telekinesis semblance to attack with your telekinesis accuracy for an attack that uses your semblance damage once and your weapon damage a second time. You can also attack using your fire manipulation semblance using the attack and accuracy from that skill once and once with your rifle weapon using weapon damage and marksmanship for the second attack. Multiple attacks are allowed but require heavy experience investment, in other words.