Wednesday, November 21, 2012

13th Age Conversion of Combat In Motion

I recently posted a review for Combat In Motion, a 3rd party supplement for D&D 4E that layers some new "houserules" onto the game which attempt to better model the game world and/or dramatic structure, in addition to providing some interesting tactical considerations.  Though the rules in the book are specific to a grid-based game with a high tactical combat component, many of the principles are of general interest from a perspective of game design.  For example, how can the weaknesses of turn-based systems be addressed while still retaining a playable structure?  Several new mechanics strive to address this goal, some of which are fairly novel to the realm of tabletop gaming. 

I'll briefly get to the heart of many of the new concepts.  Continuous motion is addressed by allowing previous moves to affect future moves, rather than allowing movement to be broken into "stop and go" segments defined by arbitrary "turns" which exist only for the sake of playability, and not in the imagined game world.  New off-turn actions allow players to react to continuous motion in more believable ways; no longer can vast distances be covered without giving opponents the opportunity to respond.  Off-turn actions are designed to not break the action economy, but rather switch things up a bit by allowing players to attack outside of their turns ("borrowing" actions from future turns).  This keeps players engaged throughout combat, since the opportunity for tactically significant action can come up at any time.  Some of these actions also grant players more freedom to manage their own offense vs defense in tactically interesting ways.  Finally, strict adherence to a randomly generated initiative order is discarded; rather, the order in which combatants take their turns depends on the dramatic context and ever-changing momentum of the battle.  Quite simply, it's a more effective way to tell a story. 

While the specific rules that address these concepts will not be applicable to systems other than 4E, it's not too much of a stretch to adapt the content using the framework of a different system.  In this case, 13th Age (which you can pre-order here).  In addition to being a game that I have a lot of personal interest in currently, it makes a good first attempt for several other reasons.  It's similar enough in that it's a d20 game with a lot of 4E inspiration, but other than that it has very different priorities.  It boasts simplified, sometimes free-form rules, prioritizes story elements, and is gridless.  Clearly a direct port with minor tweaks isn't going to happen!  Some rules will best be left ignored, while others will be simplified to some extent.  Instead of trying to make the existing 4E mechanics work within a different system, I'll instead try to write rules and make changes with the "spirit" of the concepts in mind. 

Note that the following conversions are a work in progress, and may be subject to change as the ideas are refined.  I haven't playtested any of this yet, but hopefully that will change in the near future.  Some of these things can possible stand to diverge from the original 4E rules a little more, but I feel that it's a good starting point.


Not applicable for the default TotM play style.  Ignore this chapter.


Most of this chapter is possibly too "crunchy" for 13th Age.  For players who want to sacrifice a little simplicity for the advantages of modeling continuous movement, my conversion of the rules is as follows.

For alternative solutions and deleted rules blocks, see footnotes 1, 2, and 3.

Extended Moves
The conceptual value of the Extended Move mostly lies with the interaction with Outpace and Interdict (Chapter 3).  The biggest issue that the authors were trying to solve were combatants covering a lot of ground without giving their opponents an opportunity to react.  The best solution would be to preserve that intent while honoring the system's tendency toward simplicity. 

To that end, perhaps the Extended Move rule can be distilled down to the following:  whenever you move toward a far away target (such as by using a double move) you are considered to be in-motion and your movement may trigger the Outpace and/or Interdict action

  • -While in-motion your vision is limited; treat the entire battlefield except your forward-facing direction as if you were Dazed (apply the penalty to any Perception-type rolls as well as attacks).  Your forward-facing direction includes the object, creature, or space that you're moving toward and anything directly in-between (replaces "your vision is limited" rules of the 4E version).
  • -Gain +2 to melee attacks against engaged enemies in your forward-facing direction (replaces "gain combat advantage" rules). 
  • -If you are subject to an area attack targeting a number of creatures in a group (or all creatures engaged), make a normal save (11+) to avoid all effects of the attack (replaces "retreating target" rules). 
  • -You may pop free from any engaged enemy directly in front of you if you make a move starting in-motion (no disengagement check necessary) (replaces "move with momentum" rules). 
  • -You cannot reverse direction from the previous move that you ended in-motion (replaces "can't reverse" rules).

Can be used as-is; the concept is inherently simple and intuitive.


This chapter introduces the concept of off-turn actions, as well as follows up with the consequences for last chapter's Extended Move (Outpace and Interdict).  All five rules blocks for this chapter are retained (in an altered form).

Sapped and Tapped
Remove references to flanking, otherwise these remain unchanged.  Very easy to remember, and the conditions are basically "placeholders" reminding you that you've borrowed an action from your upcoming turn.

Off-Turn Actions
Technically the first 2 bullet points just explain how individual off-turn actions will be described in their own rules blocks.  Worth keeping in mind, though it does "clutter up" this rules block a bit, making it look more complex than it is.  Delete reference to charging.  Change "must not be dazed, stunned, surprised, or unconscious" to "Must not be Confused, Stunned, or unconscious."  Change "immediate and opportunity actions" to "interrupt actions and opportunity attacks."  While this rules block is necessary background information, for general reference you'll be referring to the individual actions.

Use the rules block as-is, with the following changes.  The last sentence of the second bullet point should read "you can't engage with motionless enemies."  The third bullet point should simply read "you cannot outpace if you're engaged or otherwise unable to move." 

Use the rules block as-is, with these changes.  The second bullet point should read  "Effect:  make a single ranged weapon attack (basic attack with no frills) or cast a single-target ranged at-will spell.  On a hit the target must roll a normal save (11+) for its next move action; on a failure it doesn't reach its destination (your attack slowed it down)."  The third bullet point can be edited thus:  "you can only interdict if you are able to make a ranged attack (i.e. not stunned or unconscious), and only if you're unengaged."


The Sprint action is the most important point in this chapter for the purposes of this conversion.  Unfortunately, as-written in contains a lot of references to both grid-based movement and 4E mechanics not present in 13th Age.  It's also a little complex.  Therefore, I've completely re-written the rules block.  Also, see footnote 4 regarding Soar/Cruise.

  • -You must complete a sprint action in-motion.
  • -Your turn radius is limited to a generally straight path (as a guideline, you cannot round corners with a 90 degree turn, but you can get around them if approaching from a diagonal.  GM has final say on what constitutes too sharp a turn).
  • -While sprinting your vision is limited; as with the In-Motion state, treat the entire battlefield except your forward-facing direction as if you were Dazed (apply the penalty to any Perception-type rolls as well as attacks).  Your forward-facing direction includes the object, creature, or space that you're moving toward and anything directly in-between. 
  • -You are considered Vulnerable to any melee attacks (including opportunity attacks), and to ranged attacks made generally parallel to your line of motion (shooting at you from ahead or behind). 
  • -Ranged attacks against you made perpendicular to your line of motion are penalized as if the attacker were Dazed.  The GM has final say over whether an attack is made from parallel or perpendicular (there is no in-between), but as a general rule should favor ruling perpendicular.

The tactical consideration to keep in mind with Sprint is that it affords the opportunity to make a quick dash to present yourself as a moving target that is harder for ranged enemies to hit.  If you don't think that such tactics add to your game, feel free to ignore it.  It's recommended if you use Chapter 5, though, since the defense it provides against ranged attacks balances well with the primarily melee-centric active defenses and counter-offensives.


This chapter might be too complicated for a game run using Theater of the Mind.  13th Age is already very liberal in how you describe combatants moving around the battlefield, and there aren't really grid-based mechanics that restrict that dynamic duel feeling.  But there are also no mechanics (outside of the Rogue class) that specifically encourage it, either.  Adaptations of this chapter are worth experimenting with, and if they're too crunchy ignore them.  These are my recommendations for each of this chapter's mechanics.

Hit Point Healthy
Use a simple 3/4 HP adjustment instead.  You're really just trying to avoid prolonging battles by offsetting the increase in durability that active defenses afford both the PCs and monsters.

Re-write the rules block as follows.  Off-turn Move action.  Trigger:  Your AC is targeted with a melee or close-quarters attack.  Effect:  if you're engaged with only 1 enemy, pop off and take a move (you're sapped until the start of your next turn).  You cannot use this move to engage with any foe.  Reduce the damage taken by the triggering attack in half.

Re-write the rules block as follows.  Move Action on your turn.  Follow an Evading enemy.  If you succeed at a Hard save (16+) then the evading enemy is tapped instead of sapped.

In the first bullet point, replace "Fortitude or Will defense" with "Physical or Mental Defense."  Delete the third bullet point.

Delete this action altogether.  There's no prone or forced movement in 13th Age.

In the second bullet point remove references to prone and forced movement.  Remove the 3rd bullet, and in the last bullet change "you're tapped..." to "you're tapped and vulnerable...".

I decided to add this back in because there are specific corner cases (Hold Person spell, grabs) where an Evade couldn't be used, so it actually is useful as a last resort.

Remove references to prone and bloodied.  I'm not sure if this action is needed, as I'm not sure if auto-damage is quite the problem in 13th Age as it is in 4E.

Re-write the rules block as follows.  Off-turn Move action.  Trigger:  An attack misses you.  Effect:  Make an unmodified basic melee attack against the creature that missed you.  You can't ripost if you can't otherwise make attacks.  You are sapped until the start of your next turn. 

Note that Evade, Press, and Ripost work together quite well to model dynamic, 1-on-1 duels and provide significant tactical choices without necessarily requiring teamwork.


This chapter breaks the "don't sweat the modifiers" advice in the 13th Age rulebook, but for those who like situational modifiers the option should be there.  Everything can pretty much be used as-is, though for the Support option "Fortitude and Will" should be replaced by "Physical and Mental Defense."

Higher Ground
Change to the following:  If the target has higher ground you take a -2 penalty to attacks that target AC or Physical Defense.  GMs should use this bonus sparingly, and only in dramatically appropriate situations where terrain advantage would be significant (i.e. fighting on a staircase).

Lower Ground
Change to the following:  If the target has lower ground you gain a +2 bonus to ranged attacks.  GMs should use this bonus sparingly, and only in dramatically appropriate situations where terrain advantage would be significant (i.e. firing from a rooftop).

Precarious Position
Change to the following:  If the target is near a hazard (like a cliff) or occupies challenging terrain (i.e. waist-deep water) and you are not, you gain a +2 bonus to melee and close quarters attacks.  GMs should use this bonus sparingly, and only in dramatically appropriate situations where terrain advantage would be significant.

Optional - Circumstantial Advantage
If you want to stay true to the "don't sweat the modifiers" clause, you can substitute these bonuses/penalties for the Advantage/Disadvantage system from D&D Next. 


Dramatic Direction is arguably the most universal concept in Combat In Motion.  I also think it has the most stylistic importance.  Given that 13th Age has an inclination toward story game elements, why not employ a concept designed to structure action in a way that preserves narrative flow? 

Called to Action
This is the simplest dramatic direction both conceptually and mechanically.  I'm a huge supporter of this one, as it breaks combat up into dramatically relevant "scenes" instead of resolving actions as a randomly-determined jumble.  Causal relationships aren't always clear when you interrupt the action with someone else's turn.  No reason not to use this for any RPG with a numerical initiative system.  The rules block works fine as-is for 13th Age.

Keep Rolling
This only matters if you're using Motion States.  Basically, characters who are already committed to an action (by virtue of their being in the middle of it) should go first.  Their momentum would give them a temporal advantage, and it makes narrative sense to resolve their actions as soon as possible.  The rules block is fine as-written.

Held in Suspense
Change the trigger to the following:  You're Held in Suspense if subject to the Stunned condition, if you're prevented from moving (such as by a spell or power), or if you've suffered a physical setback (such as falling off of a horse) before you've taken your turn this round. 


1:   Crunchier Alternative to Extended Moves:  One solution is to use the rules block for "Change Your Motion State" and "Extended Move" as is.  These rules aren't too crunchy, and mostly set the stage for the real meat of this chapter -- the In-Motion state and its bonuses and penalties.  They're intuitive enough that once you get the general idea, you can apply them without thinking too much about it. 

Though the Extended Move rules block contains 5 bullet points, for the purposes of 13th Age you can pretty much distill it down to the following summary:  whenever you take a double move on your turn (such as when attempting to reach a far away target), you must end your first move and begin the second in-motion (important for triggering off-turn actions).  Rogues need to pay closer attention, as they have standard actions that sometimes include movement components (personally I'd give them the option to change motion state or not; note that the class would get an initiative advantage via the Keep Rolling dramatic direction, which is at least thematically appropriate).  Also remember that teleportation and triggered actions can ignore motion state requirements, and you may or may not want to keep the readied action restrictions (though as a situational rule, and an extra thing to remember at that, it's safe to ignore it without impacting the intent of the mechanic too much).

2:  The "Complete an Action In-Motion" rules block is largely redundant for the purposes of this conversion.  It provides clarifications for grid-based play that 13th Age simply doesn't employ.  With a much simpler "facing" system described in the rules for In-Motion (and the system's encouragement for rulings over rules), this stuff need not be spelled out so exactly.

3:  The final concepts in this chapter are too overly-specific and situational to really worry about for 13th Age.  Forced Movement doesn't often occur with this system, and when it does squares aren't counted because play is gridless.  Likewise the effects of Stumble and Crash are mostly irrelevant.  The fact that Teleportation works a little differently as its movement isn't directly dependent on motion-state might be worth remembering, but the specifics (placement of the Trail and such) are irrelevant to this conversion.

4:  I'm not even going to bother with conversions for Soar or Cruise.  Not only will flight and vehicles/mounts possibly be covered in 13 True Ways, but these rules are very situational and quite crunchy.  Not the best combination for inclusion into 13th Age.  The gist of Soar is that when GMs are describing creatures in flight, do so in a way that makes sense.  Don't exaggerate their maneuverability, and make them actually keep moving (unless they can specifically hover).  Likewise, describe vehicle movement in a way that makes logical sense.  The existing range band system doesn't model acceleration very well, so don't worry about it.  Use cinematic narration and existing mechanics (skill checks) for things like chase scenes.


  1. First Revision: Added Cower back in and re-wrote the Terrain section.

  2. Second Revision: Re-wrote Held in Suspense.