D&D 5E (2024) Infiltration with a familliar

I’m about to run a heist campaign in D&D rules and one scenario really bugs me. It’s when one player transforms themselves into a small spider or uses a familiar and then infiltrates the lair, unilaterally while the rest of the party have to spectate. The DM has two choices, either stop clever investigative work and risk punishing the PC. After all if that wizard’s 1hp cover gets killed the wizard is stuck solo in the middle of the zone. The alternative is the wizard getting to unilaterally explore a location while the rest of the party spectates. Few adventures are intended as solos.

Where something is useful and sensible but not much fun, my gut tells me to abstract the hell out of it. Give the info in a simple and quick way without wasting everyone else’s game time. To this end I present this subsystem for working out how things go when a familiar scopes out a location. Something particularly useful for raids and heists. The rules apply to a familiar infiltrating as much as a polymorphed character.

The infiltration takes the form of a skill challenge. With a few curve balls thrown in for good measure.

Step One - Determine a Location

The Player decides the Location to infiltrate. It might be a monster’s lair, a prison, or a or a guarded vault. The more security the location has, the harder a creature will find to infiltrate. The DM should determine a Difficulty Class for the location based on the locations structure and surroundings, the likelihood of being caught and how likely it is for the infiltrating creature to be found in that area.



The DM should take a balanced approach and pick the difficulty that overall best fits the infiltration. However, when in doubt round up, gaining information should challenge the party. It isn’t necessary for the DM to share the difficulty with the Players if they wouldn’t have this information beforehand. Though that might be discovered by other forms of information gathering.

Step Two - Run the Infiltration

The familiar, animal companion, or summoned creature should make three ability checks in the order of their choice to determine how successful the infiltration is.

• Dexterity (Stealth): How far the creature can get before being forced to turn back.
• Wisdom (Perception): How much the creature spots from its perspective.
• Intelligence (Investigation): What the creature can infer or discover from inspection.

The infiltrator makes these three checks against the location’s DC.

• Each test that passes the DC counts as one Success
• Each successful test that rolls a natural 20 also grants one Insight
• Each test that rolls less than 5 counts as one Mishap

Alternative checks: It’s possible that other checks might be appropriate instead of Investigation (Intelligence): exploring a forest creatures lair might involve Wisdom (Survival), infiltrating a wizard’s lab might use Intelligence (Arcana).

A tactical approach: Before making these rolls the infiltrator can also decide to be Reckless, Cautious, or chart a Balanced path between the two.

• Reckless: The infiltrator can push on regardless of danger to learn as much as possible. Taking risks that mean they are likely to get caught. In this case you get Advantage on the skill checks, but the result of either roll can lead to a Mishap
• Cautious: You can be particularly careful not to get caught but that can limit the amount you can discover, in which case you have disadvantage on the skill checks, but only natural 1’s lead to a Mishap
• Balanced: Roll the checks normally.

How long does it take: Infiltration requires patience and opportunism to do properly. It takes 1 hour to properly infiltrate a location equivalent to a typical townhouse or place of business with 1-6 rooms. Larger locations take a proportional amount of extra time, with a large inn with many rooms taking perhaps 2-3 hours and a large fortification or palace taking most of the day.

The time it takes to infiltrate could be rushed in half this time but in those circumstances all ability checks are made with disadvantage. You can make a rushed infiltration Cautiously or Recklessly. Its already assumed you are being pretty reckless by rushing.

Step Three — Mishaps

Mishaps represent the things that can go wrong during an infiltration. They are worse than simply being forced to turn back and abandon the infiltration as this is covered by the limited success.

Whenever a mishap occurs the denizens know something is wrong and will be unsettled, even if they don’t know why. For the next 24 hours further skill checks for infiltration in that location are at Disadvantage and during that time guards will be more alert than normal. Add 2 to all Passive Perception stats.

To find out the result of the Mishap Roll 1d6 and add the total number of Mishaps to see what happened. Its not possible to have more than one result from a single infiltration.



Step Four - Reveal the Intelligence Gained

Assuming the infiltrator was able to relay the information either through magical means or by escaping, use the table below after the challenge to see how far the infiltrator reached and what useful information is gained based on the number of successes.

Insights: For every natural 20 rolled on a successful test the infiltrator reveals one secret about the location. This might the presence of a hidden trap or defence, how to access a secret door, a password or the location of a precious treasure. These Insights are up to the DM to determine but they should be useful and significant. The represent a stroke of luck.



I appreciate this is a long post and probably not the right space but really interested in what folks thing. Particularly those who have experienced Familiar infiltrations before. This was inspired by a recent thread about familiars and how much information to give out in that situation. As well as a recent play through of Assassins Creed Odyssey where I really liked the way his eagle companion was abstracted into the game.

What are your thoughts? How would you change it? Could it work?

I don't really have a problem with the rest of the party spectating. If a player is role-playing and has zero interest in seeing what his/her comrades can create, that player should be playing a video game instead.* The onus is on the GM and PC to make the spectating part interesting, though.

Could four steps of infiltration work? Sure. Just don't make it seem boring. The PCs don't want to hear, "hold on, I think I screwed up this table. Let me read this for a few minutes." Keep it interesting, and you can do just about anything at the table.

*Or playing an unsolo RPG.

I think part of the social contract of D&D is that you do not pick a course of action that sidelines the rest of the PCs.

sevenbastard said:

I think part of the social contract of D&D is that you do not pick a course of action that sidelines the rest of the PCs.

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Precisely.

In a heist adventure the fact finding is really important. I’m keys from the golden vault a lot of this I got is just handed to the PCs which I think is a bit of a missed opportunity.

GMMichael said:

I don't really have a problem with the rest of the party spectating. If a player is role-playing and has zero interest in seeing what his/her comrades can create, that player should be playing a video game instead.* The onus is on the GM and PC to make the spectating part interesting, though.

Could four steps of infiltration work? Sure. Just don't make it seem boring. The PCs don't want to hear, "hold on, I think I screwed up this table. Let me read this for a few minutes." Keep it interesting, and you can do just about anything at the table.

*Or playing an unsolo RPG.

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I agree it mustn’t be tedious.

I think Stage one would be picked by DM based on the location they have designed. Quick decision.

Stage 2 is the die rolling and decision step. Yes the player needs to decide who to send in to infiltrate and whether to be reckless or cautious but those are the only decision points.

Stage three is a simple die roll and only comes up on a serious fail. I’d expect there to be a bit of tension there.

Stage four is the interpretation. This is the one that is important and probably takes the most thought. If it’s a heist campaign the DM probably needs to put some thought into what they would reveal when preparing the adventure.