I am GMing for the second time in my life, and do not know how to handle this situation: There are 5 PCs who walk through this map. In almost every room there are a couple of NPCs who might or might not hear fighting in another room. So far no problem. I roll some dice to decide whether they hear it or not. But IF they hear the fighting, they want to join the battle. So how do I handle this?

Scenario: The PCs and an NPC fight in area C19. Sometime during the fight, an NPC in C23 and another in C21 want to join the fight.

Map of Thistletop / Rise of the Runelords

What would be the (new?) order of initiatives? Do these incoming NPCs have an attack of opportunity?


You're right that the basic initiative rules just kinda assume everyone's in the fight at the beginning of the battle and don't say more than that, so the addition of late arrivals requires some interpretation.

In general, as new arrivals become aware of and desire to participate in the battle, they should just roll initiative for the first round they're aware and then be slotted into the existing order.

There are no "attacks of opportunity" specifically granted by initiative or surprise; I assume you are referring to the surprise round of free single actions that happens at the beginning of a combat when some combatants are unaware of others, and during which unaware PCs are flat-footed both for the surprise round and until they act on their first round. The rules are written to describe the surprise round as only being at the beginning of combat, but it's certainly realistic to say that new arrivals might be able to come upon current combatants more or less unawares, even with the "360 degree sight" Pathfinder affords everyone.

What I do is, if the new combatants just want to charge in and fight, I just slot them into the initiative. If, however, they do want to sneak up on the fight and take someone unawares, then I use the standard Stealth vs Perception check to determine awareness from the surprise rules. If someone is surprised, I don't insert a surprise round, but I do afford flat-footedness to their unaware opponents till they act.


So for example, let's say Robilar (init 11) is fighting two orcs (inits 12 and 7). A pair of sleeping orcs, a shaman and a warrior, hear the fight in another room and go to join in. The warrior just runs into the fray, so he rolls initiative and gets a 13. At the top of the round, he runs in and chops at Robilar, with no special bonuses. The shaman decides to be sneaky and wants to peer through a door and snipe Robilar with a ray of exhaustion. He makes a Stealth check against Robilar's perception and wins, and rolls an init of 6. That's fine, Robilar goes on 11 but doesn't see him, and then the shaman zaps his flat-footed touch AC with a ray on 6, after which Robilar is quite aware of him (the orc doesn't have enough Stealth to try true sniper tricks with a hide at -20, so he just pushes the door the rest of the way open and fights normally).

In my opinion this merges rules compliance, speed of resolution, and realism of result.


I'm taking @mxyzplk's word that the official rules for Pathfinder offer no solution to your case and I'm going to cover the "what's the non official but good way to make this happen?" question.

D&D 3.5e (which PF is based upon) had this rule where people joining the fight later got to act at the initiative count they would have acted if they had rolled 1 more than the current combatant at the highest initiative count (Rules Compendium page 71, newcomers aware).
I think it's a good idea. Those guys have already been skipping some rounds, including the one where they realized something was going on in C19. It also helps you're not spending time to roll new initiative checks after the fight has begun.


My take on this would be the following (though I'm not sure whether the RAW dictates the same):

  1. Roll an initiative for everyone - including those in C23 and C21, in this specific situation - at the beginning of the fight. (To speed up combat, roll a single initiative score for any and all "unexpected combatants" as well, and use that for anyone/everyone entering combat without you having planned so. Mind you, you can, with some clever and imperceptible railroading, prevent most such totally unexpected parties from entering combat... but that's a different question.)

  2. Each round - when it's their time to act in the initiative order - roll perception for the NPCs (in C23 and C21, in this specific situation) to see whether they notice the fight.

  3. When/if they notice it and decide to join the fray, have them take their turns as per the standard rules for initiative. They'll need to spend move actions to get there, open doors, etc.

  4. Whether these NPCs will get AOOs (or be subject to AOOs themselves, because of arriving in a threatened area, for example) depends on the exact situation upon their entering, which is impossible to predict. (The many factors: position and initiative of PCs and their opponents, situational modifiers, (N)PC abilities, etc, etc.) Use the standard rules.

  5. I would not consider anyone flat-footed after the initial surprise round. Even if the NPCs entered the room without drawing anyone's attention, the best they could hope for when attacking would be a flanking bonus (and a possible sneak attack for rogues.) The reason for this is that everyone inside is already fighting, and expecting attacks from practically any direction - how well they react to a new threat depends on their Dex score (among other things), and I see no reason to deny that to any side.

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    \$\begingroup\$ @OpaCitZen This is answering the specific situation here, where all of the possible combatants are known. What about in the general situation, where originally unknown combatants could become involved? You can't roll initiative for the entire world ahead of time... \$\endgroup\$ – YogoZuno Apr 13 '14 at 22:33
  • \$\begingroup\$ @YogoZuno First of all, this Q asked specifically for this. (Ask a new Q if you want answers for a significantly different scenario.) Second, as I've already said, there are no originally unknown combatants for the DM. Also, the entire world is rather unlikely to enter a single combat scene in D&D - but even if it did, it would be the DM's doing. Should that happen, the DM should (that is, if I were that mad DM, I would) roll a single initiative for the entire world. Simplify things and rules. Speed up combat. Don't let the game get bogged down. \$\endgroup\$ – OpaCitiZen Apr 13 '14 at 22:45
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    \$\begingroup\$ @OpaCitZen - Read the actual question title. That is asking the general question. The specifics in the question are simply an example. Sure, you can just answer that specific scenario, but answering the general situation would make for a more useful answer. As to unknown combatants - there can always be unknown combatants in an open world. Maybe the players do something the GM didn't consider to involve innocent bystanders, or maybe the players move the combat to an unanticipated location due to cleverness. The GM is not actually omniscient. \$\endgroup\$ – YogoZuno Apr 13 '14 at 22:53
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    \$\begingroup\$ @YogoZuno Read point 1 of my A, again. It contains my general answer. Sure, the DM is not omniscient. However, the DM is almost omnipotent (at least in 3.x/PF.) Should she/he allow unanticipated combatants into a fight (instead of very subtly & imperceptibly railroading the situation), she/he should roll initiative for the new combatants and enter them into the initiative order. (See my reply to your first comment.) But the DM could actually roll an initiative for "any/everyone who enters combat unexpectedly" at the beginning, and use that. Expect the unexpected, speed up combat. \$\endgroup\$ – OpaCitiZen Apr 13 '14 at 23:09

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