I've been making a design document for Hammercalled recently to give some guidance to people who want to tinker with the system and help me realign all the rules to stated practice.

Part 1 focused on the dice mechanics, but today I'm going to talk about the ways in which the GM can use the mechanisms to interact with players and the game universe.

GM Toolset

The GM doesn't follow the same set of rules as the players; their rules are fairly simple and revolve around providing interesting scenarios for the players. They manage NPCs, set TNs, and play a key role in the narrative, though they interact with the world in a very different way than players do.

NPCs

NPCs function as highly simplified versions of characters, with a couple combat statistics and IAATs that are intended to show what they can do outside combat (which only matter with regards to the players).

Because of how this works, the GM is freed from worrying about excessive bookkeeping (you can abstract NPCs out entirely except for combat and just have players make rolls with appropriate modifiers as determined by the GM), and it also helps to make sure that the GM is discouraged to step on the players' toes by bringing a support character along and then getting bogged down in the action.

Unless it involves a player, the GM never rolls for a test, and even then players typically do the rolling (initiative, status effect removal, and NPCs healing PCs are rare exceptions to this rule; even NPCs attacking PCs is handled as a defense roll by the PC).

Setting TN

The GM's greatest tool in play is setting the TN modifier. This is both incredibly quick and incredibly important. The GM can use whatever methods they see fit, but we generally recommend balancing in a method that reflects some concessions to reality while keeping the story moving.

The GM's goal is to co-tell a story, so the TN modifiers they apply should be used to retain some level of consequence to actions while also providing opportunities for players to drive forward; the GM is like track guiding a railway-car; the people in the car want it to go somewhere, and the track should ideally get it there safely. Adding additional quality to the experience comes down to the GM's skill in this and other areas, but a minimally proficient GM should be comfortable with this.

Themes

The Themes system allows the GM to set a number of topics for the game to follow, then reward players. It's strictly a matter of communicating what's happening, and may be removed as it adds confusion but doesn't necessarily do anything you can't do elsewhere.

Risks & Rewards

The GM is encouraged to offer rewards in the form of circumstantial modifiers, Destiny, resource restoration, XP, talents, and short-term gear.

In addition, many of these are offered through the other game mechanics, such as the ongoing resource economy.

Destiny

Destiny is a "get out of jail free" card, and allows players to do whatever they need/really want to do within reasonable limitations.

The counterpoint to this is that while Destiny literally lets players take over for the GM for a moment, it's very limited in terms of availability.

To keep this at an appropriate pace, the GM is the sole gatekeeper of Destiny, allowing them to reward players who are following the storyline by letting them have more points with which to push the storyline forward, while players who are spending Destiny frivolously lose some narrative control they could expend elsewhere.

Gear

Gear in Hammercalled is a major defining trait for characters, but small pieces of gear or plot-relevant gear can be given out as needed. For instance, the GM generally can say that people have something (for instance, flashlights), whether or not they planned on having it.

The GM can temporarily confiscate gear (e.g. when the characters are in prison), but they can also give players more access to gear to give them a boost, temporary or otherwise. This should be done sparingly in many situations, but as players develop their own personal gear the reliance on environmental gear will decrease; this found gear is a great way to prevent story stagnation.

Temporary Resources

The temporary resources (damage, wear, and status effects) are all things that interact with characters. While they have limited actual effects on a character's overall long-term performance, they do have an immediate effect on short-term performance, either in the form of increased aversion to future risks (Stamina damage and the first two levels of wear) or penalties (Wounds and the last level of wear) that are immediately applicable to a character.

The GM is the primary source of this sort of thing, though wear is a result of player actions (since the GM determines when a player should roll or when their actions succeed automatically, this comes into play relatively frequently).

Damage

Damage occurs during combat when a character suffers an incoming hit or outside of combat when they attempt an action that fails in a way that makes sense to cause harm to their person.

Unlike a PC's outgoing damage, incoming damage is always based on a number set by the GM, and can be adjusted as needed; this is typically done by choosing a static number and then taking an inverse margin.

Due to the way an inverse margin is handled, incoming damage can be lesser than PC damage and still have a significant impact, as only a result of 100 results in a 0 Margin.

This quirk is offset by the effects of Wear in most cases.

Wear

Wear is an important factor in handling the resource economy and providing a limit on players. Generally the philosophy is that player should be able to do as much as they want of what they're good at, but once they start abusing their power they get into trouble.

For instance, there is a talent that allows people to reroll failed Immediate Aid, which means a first aid kit will almost never take wear in their hands.

The counterpart to this is that the Immediate Aid process has intrinsic limitations.

Wear happens roughly 10% of the time, ranging from 20-3%, given special circumstances. This means that a character who is optimizing the Attribute+Specialization+Talent+Gear combination can only, on average, do things that cause Wear 15-30 times before they are likely to have accrued the three points of Wear needed to render gear inoperable.

The GM can also cause Wear in special conditions or as a penalty for misuse, which serves to encourage players to invest their resources toward driving the plot forward.

Talents & Flaws

Talents, like gear, represent an area where the GM shares some control with player, but in which the player gets to make a majority of decisions but it is ultimately the player who determines the thrust of their character's development.

During play the GM is encouraged to give players talents or flaws, especially ones that represent the decisions that players have made. Rather than following the list, a GM can create a talent specifically for the players collectively or individually, and this is encouraged.

The reason why this is important is that it serves as an immediately associated reward–a trophy–for good storytelling actions, and it also provides an element that is not easily mechanically duplicated. Of course, Talents that provide a simple mechanical bonus exist, but tend to be fairly conditional to prevent a character from using them simply to be the best in one particular area. They are not as interesting as "fluffy" talents, generally.

XP

XP is a difficult element to balance. On one hand, Hammercalled is built to scale well with a variety of characters (although characters weaker than the default definitely encourage lower-stake play with fewer difficult tests), but it is also likely to face some potential balancing problems down the road.

A couple reasons for this are as follows:

Attributes go very high, and contribute to derived attributes. This can make high-power characters demigods very quickly.

Specializations are capped, and at a relatively low value. This means that strong characters tend to be forced to develop as generalists, not specialists. This could change in later versions of the game, but doing so with the current XP to bonus rate would mean that a character could stack a specialization very high relative to other characters.

Talents are a means of differentiating characters more so than adding power, and having too many characters with the same talent reduces the agency that any individual receives from having that talent (typically; the combat talents are more power-building than depth-adding in most cases).

Gear is nominally self-balancing, but this is only because each piece of gear has its own costs and is useful only in certain applications, so investing XP in gear represents a direct trade-off to more general and universal benefits. In practice, this may not function as designed, and some gear qualities may be exacerbating this.

In any case, the rule for XP is that it should take 5 XP to get to the point of making a meaningful change (e.g. a 1-2 point boost to actions or an improvement to a piece of gear), and no less than 25 XP to get significant changes (e.g. getting a decent score in a new Specialization, increasing an attribute by ~7 points, adding a new and powerful piece of gear).

This is in line with the notion that a GM should typically award 1.5 XP per hour of play, plus up to an additional .5 XP in bonuses (I don't state this in clear mathematical terms, instead leaving it in a more vague suggestion so GMs feel free to experiment).

My estimate is that it takes roughly 180 XP for a character to become an unrivaled master of a particular pursuit, and characters probably become legendary in multiple fields at the 400-500 XP point. Hammercalled currently doesn't do anything to prevent people from becoming strong in many different areas, though party composition should serve as a soft redirection away from duplicating distinct strengths. Right now, the core Rules Reference content includes four or five specific domains. In something like Unsung Gods, where there are magic systems and setting-specific talents, characters can probably continue meaningful development 20-100 XP further down the road.

Many talents function on an "opt-in/opt-out" basis, meaning that they make certain mechanics easier for characters or allow a character to ignore them in most cases (like the Gear Cautious trait).