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As a player (or DM) might use a familiar as a spy, are there ways, magical or otherwise to detect that a cat is a familiar, or just a house cat?

I've read the answer to Are familiars considered magical for effects like detect magic? and agree with the accepted answer that they are not. So what might be other methods for exposing the nature of the creature in front of you?

And I mean short of killing it to see if it disappears ;)

NotArch
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James
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1 Answers1

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Detect Evil and Good

The spell detect evil and good will allow you to determine if a beast has a creature type consistent with a familiar:

For the duration, you know if there is an aberration, celestial, elemental, fey, fiend, or undead within 30 feet of you, as well as where the creature is located.

This works, since find familiar states:

Appearing in an unoccupied space within range, the familiar has the statistics of the chosen form, though it is a celestial, fey, or fiend (your choice) instead of a beast.

This won't explicitly tell you "this creature is a familiar", but if you know anything about familiars, you will know that a celestial, fiend, or fey appearing as a harmless beast will be rather suspicious; suspicious enough to say "this is probably a familiar".

Locate Animals or Plants

The spell locate animals or plants can tell us what need to know:

Describe or name a specific kind of beast or plant. Concentrating on the voice of nature in your surroundings, you learn the direction and distance to the closest creature or plant of that kind within 5 miles, if any are present.

With this one, if you suspect a nearby cat may be a familiar, cast this spell and concentrate on cats. If the suspicious cat pings with the spell, you know it isn't a familiar.

Channel Divinity: Arcane Abjuration/Abjure the Extraplanar (require a saving a throw)

These are conditioned on the suspected familiar failing a wisdom saving throw. The Arcana Cleric's Channel Divinity Arcane Abjuration says:

As an action, you present your holy symbol, and one celestial, elemental, fey, or fiend of your choice that is within 30 feet of you must make a Wisdom saving throw, provided that the creature can see or hear you. If the creature fails its saving throw, it is turned for 1 minute or until it takes any damage.

The Oath of the Watchers Paladin's Abjure the Extraplanar ability reads:

You can use your Channel Divinity to castigate unworldly beings. As an action, you present your holy symbol and each aberration, celestial, elemental, fey, or fiend within 30 feet of you that can hear you must make a Wisdom saving throw. On a failed save, the creature is turned for 1 minute or until it takes damage.

These aren't totally reliable, as they require a saving throw.

66% of the time, it works every time.

There are a few options for detecting fiends and celestials that do not detect fey. These include:

  • The Paladin's Divine Sense feature.
  • Helm of the Gods (from Mythic Odysseys of Theros)

Additionally, the Oath of Ancients Paladin's Turn the Faithless channel divinity turns a fiend or fey on a failed saving throw, but has no effect on celestials. The Oath of Devotion Paladin's Channel Divinity turns only fiends.

Thomas Markov
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    @DarthPseudonym There were a couple of other options that worked for celestial and fiend that missed fey. 66% of the time it works every time! – Thomas Markov Feb 19 '21 at 16:15
  • Great option. It might be worth adding that if they don't have access to this spell, the higher level Locate Animals or Plants could similarly help. – Gandalfmeansme Feb 19 '21 at 17:26
  • Awaken also works, though it's perhaps a bit excessive. Dominate Beast, Animal Friendship... many of these would do the same – Ben Barden Feb 19 '21 at 17:29
  • Oddly, Locate Animals or Plants might not work. After all, "cat" is a kind of beast (and can thus be selected) and the familiar is a creature that is a cat. The only thing that changes is that it's not a beast. So is a cat that happens to not be a beast the same "kind" as all the other cats? That seems like a matter that at least invites DM adjudication. – Ben Barden Feb 19 '21 at 17:46
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    @BenBarden The cat not being a beast makes it an inelligible target for the spell since the spell finds beasts and plants, not fey, celestials, or fiends. – Thomas Markov Feb 19 '21 at 17:49
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    @ThomasMarkov but the spell text does not say that it only finds beasts and plants. It says that it finds creatures and plants that are of the given kind. So, for example, if you somehow had a plant that was a cat, and you searched for cat, it seems like you'd find it. I admit that there's at least an implication that it would skip over non-beast cats, but I assert that it's not entirely clear, and could be reasonably interpreted either way. – Ben Barden Feb 19 '21 at 17:52
  • I love the idea of using Locate as detection by contradiction. – Darth Pseudonym Feb 19 '21 at 18:13
  • +1 for Locate Animals or Plants because it is a Ritual as well, so potentially more handy as will not expend a spell-slot for any ritual casters :) – Thank-Glob Feb 19 '21 at 23:43
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    A DM who has introduced a real small beast might have it reacting by running away anyway if abjured - I don't imagine the "presenting" involved is supposed to be done in a way that would otherwise be inviting or playful. Although there could also be comedy value in having the cleric burning with holy fire, yelling "away foul creature of the abyss" and having whatever creature approach and sniff the holy symbol to check whether it is some kind of treat :-). – Neil Slater Feb 20 '21 at 11:35
  • I'd also note that a failure with abjuration might also work partially as a detection, depending on DM. I'd definitiely consider it - although saving throws determine mechanical outcome, there is an implied test of wills (or for other saves fast reactions etc) that means the narrative does not need to be "it works" versus "nothing happens" - a valid abjured target familiar might stare balefully, hiss, raise its hackles etc as it contests a cleric's will. Of course, a real housecat may do the same – Neil Slater Feb 20 '21 at 11:37
  • In PHB pg 185, the description of Truesight indicates "perceives the original form of a shapechanger or a creature that is transformed by magic." Has the fey/fiend/celestial been "transformed by magic" and accordingly it's original fey/fiend/celestial form would be perceived? – Weiramon Feb 24 '21 at 17:00
  • @Weiramon That sounds like a good question to ask. – Thomas Markov Feb 24 '21 at 17:15