The companion piece. If you want the full rules, the wild fifty-year name history, and the whole 2014 versus 2024 breakdown, that’s all in the Detect Evil and Good explainer post. Go read that first, then come back, because here we’re answering the only question that matters with this spell: now that you know it doesn’t do what its name says, what is it actually good for?
This is the spell everyone misreads. So before a single use, let’s nail the myth to the wall and leave it there.
Detect Evil and Good does NOT detect evil. It does NOT detect good. It does not read alignment, it does not out the lying noble, it does not tell you the shopkeeper is a wrong ‘un. What it does is sense six creature types within 30 feet, aberration, celestial, elemental, fey, fiend, and undead, plus their location, and it senses ground that’s been magically consecrated or desecrated, which in 2024 means the Hallow spell. That’s the entire spell. Every good use below flows from that one true fact, and every bad take you’ve heard flows from ignoring it.
REAL USES (rules-solid)
1. Radar through the wall. This is the headline use and it’s pure RAW. The spell reaches through most barriers, so you feel the undead, fiend, or aberration in the next room before you open the door. It’s stopped only by a foot of stone, an inch of metal, a lead sheet, or a yard of wood or dirt in 2014, and it’s blocked a little more easily in 2024, but through a normal door or interior wall, you know what’s waiting. Walking point in a crypt with this up is one of the best things a first-level slot does. (Grounded in RAW, PHB p231.)
2. Out the fiend in the nice suit. Here’s the use that actually justifies the name. A creature disguised by mundane means, a hood, a cloak, a good hat, is still a fiend underneath, and its type is what pings. So the friendly blacksmith who lights up your detector like a pit fiend is telling you something the town doesn’t know. A whole D&D Beyond thread landed on exactly this: neither this spell nor a paladin’s Divine Sense reveals alignment, but both flag creature type, so a devil or celestial hiding in a crowd of humanoids stands right out. (D&D Beyond forum) And r/DnD has the perfect example in the wild: a party sweeps a BBEG’s airship, the paladin’s spell flags a lieutenant as an elemental, and the disguise crumbles because a phoenix wearing a human face is still an elemental to your radar. (r/DnD, “My players are really dumb when using ‘detect evil and good’ (5e),” r/DnD)
3. Find the invisible thing. The spell gives you location, not line of sight. So an invisible imp, a hidden lurker aberration, or an undead creeping through fog still shows up on your 30-foot sweep, and you know roughly where it is even when your eyes get nothing. That’s a genuinely strong counter to ambush predators from those six types. (Grounded in RAW.)
4. Trip the Hallow wire. The second clause of the spell senses consecrated or desecrated ground. In a dungeon full of cultist altars or a temple someone has defiled, you feel the sanctified or profaned area before you blunder into whatever it’s protecting or powering. In 2024 this is specifically your tripwire for an active Hallow spell. Niche, but when it matters it matters a lot. (Grounded in RAW.)
5. Ten whole minutes of coverage. Duration is the underrated stat here. Ten minutes of concentration is enormous for a first-level spell, long enough to sweep a floor of a dungeon, cross a graveyard, or hold it through a tense parley with a suspicious envoy. You cast once and stay lit up the entire scene. (Grounded in RAW.)
6. Know which “detect” you’re holding, versus Divine Sense. If you’re a paladin you’ve got both, and they’re not the same tool. Divine Sense reaches 60 feet but only catches celestials, fiends, and undead, costs an action, uses a limited daily pool, and needs no concentration. Detect Evil and Good reaches 30 feet, catches those three plus aberrations, elementals, and fey, costs a spell slot and concentration, and runs for ten minutes. Divine Sense is your quick pulse, the spell is your sustained sweep with a wider net. Pick by the job. (D&D Beyond forum) A r/DnD thread asking whether a paladin would ever bother laid out the same math point by point: the spell catches roughly double the creature types, sees through solid surfaces, and eats a cheap first-level slot instead of your daily Divine Sense pool. (r/DnD)
7. Confirm the impostor is not a person. You suspect the missing duke came back wrong. Sweep the room, and if the “duke” pings as a fiend or fey, you’ve confirmed a shapechanger without accusing anyone out loud. You still won’t know exactly what he is, only that he’s one of the six, but that’s usually enough to change your whole plan. (Grounded in RAW.)
CHEESES (clever, and legal)
8. Pre-scout the boss room. Because it sees through a normal door and lasts ten minutes, you can stand outside the sealed chamber, sweep it, and count nothing, or feel that yes, there’s undead in there. Cheap threat assessment before anyone rolls initiative, no trap door opened, no ambush walked into. (Grounded in RAW.)
9. The wider net beats Divine Sense for weird dungeons. Aberration, elemental, and fey are exactly the types that don’t show up on a paladin’s Divine Sense, so in a Feywild jaunt, a mind flayer colony, or an elemental plane, the humble first-level spell quietly outperforms the flashier class feature. Prepare it specifically for those campaigns. Ask the r/DnD player who begged fellow paladins to pity “us poor souls who found themselves in an Aberration-based campaign,” where Divine Sense goes blind and this spell is the only thing that still sees the enemy. (r/DnD)
10. Passive shapechanger screen at court. Hold it through a diplomatic scene and you’re running a silent background check on everyone who walks within thirty feet. A rakshasa fiend or a disguised fey ambassador can talk their way past your Insight check all day, but they can’t talk their type out of your radar. (Grounded in RAW.)
QUESTIONABLE (ask your DM, argued to death)
11. The mother of all mistakes, “I detect evil on the NPC.” This is THE argument, and it comes up constantly. A newer DM let their cleric use Detect Evil and Good to sense an NPC’s “evil intentions,” the table ran with it, and then the DM realized the spell does no such thing and had to walk it back. The forum verdict was blunt: the spell only flags the six creature types, a human villain never pings no matter how evil, and if you want alignment-sensing you’re homebrewing a different spell. Settle this at your table before someone builds a plan on a lie. (D&D Beyond forum) The same principle settled a r/DnD question about a Dhampir PC surrounded by holy orders: does their deathless, half-vampire nature light up the radar? The table answered flatly no, because a Dhampir’s creature type is humanoid, so the spell and Divine Sense both slide right past them no matter how undead they feel. Type is the only thing the spell reads, full stop. (r/DnD)
12. Does a magically disguised fiend still ping? This is the real gray zone. A creature under Disguise Self or a Hat of Disguise hasn’t changed its creature type, only its appearance, so by a strict reading it still shows up as a fiend on your sweep. Most tables run it that way. But note the spell has no clause about detecting that magic is being used to hide something, it just reports type and location, so your DM decides how loud that ping is and whether the illusion muddies it. (Grounded in RAW; common table reading.)
13. What about actual shapechange or true polymorph? Here’s the flip side of the last one. If a devil uses a real shapechange or is hit with True Polymorph and genuinely becomes a different creature type, then there’s a strong argument it no longer pings as a fiend at all, because type is the whole hook. That’s a DM call every time, and it’s the loophole a clever villain uses to walk right past your detector. (Grounded in RAW; DM-dependent.)
14. Old-edition brain, and why your veterans expect more. If someone at your table swears this spell should read alignment, they’re not crazy, they’re just remembering third edition, where Detect Evil literally scanned auras and told you how evil something was over a few rounds. Whole threads exist of players relearning that fifth edition quietly deleted that function. Worth knowing so you can head off the argument with history instead of a rules fight. (EN World)
15. It gives away that you cast it. Small but real. The spell has verbal and somatic components, so anyone watching or in earshot sees you cast something. Against a savvy disguised fiend, casting Detect Evil and Good at the dinner table might tip your hand before your radar even resolves. Subtlety costs metamagic. (Grounded in RAW; raised in the D&D Beyond “question” thread above.)
16. The DM has answers for your radar. Worth knowing before you lean too hard on the sweep. A r/DMAcademy favorite crowns Nystul’s Magic Aura as the most underrated low-level spell precisely because its Mask effect lets a DM pick what creature type your Detect Evil and Good reports, so the fiend behind the throne can read as a perfectly boring humanoid. (r/DMAcademy) Over in r/CandlekeepMysteries a DM running The Price of Beauty fretted that eager paladins sensing everyone at the door would spoil the hag mystery, and the table’s fix was an Amulet of Proof against Detection and Location handed out like temple uniform, quietly shutting your divination down. (r/CandlekeepMysteries) Your radar is strong, but it is not the last word.
DEVIANT, FUNNY, AND CURSED
17. The lawful-stupid paladin special. The eternal bit. A brand new paladin strides up to the shifty-looking rogue, proudly casts Detect Evil and Good expecting the villain to glow red, and gets absolutely nothing, because the rogue is a person and people don’t ping. It’s a rite of passage, and it’s the single most common way players learn what this spell actually is. Do not be that paladin. And do not be the r/DnD cleric who, told the spell was triggering, walked up and demanded “why are you a celestial/fey/fiend/aberration/elemental/undead,” picking a fight with a disguised phoenix and then wondering aloud why the party keeps getting into so many fights. (r/DnD, the same airship thread cited at use 2 above)
18. Your bard was the monster all along. Cast it in a quiet moment and discover the fey creature within thirty feet is, uh, your own party’s feywild-touched bard, or the warlock whose patron did something weird to them, or the reincarnated druid. The spell doesn’t do politics, it does types, and sometimes the type it finds is sitting on your side of the table. (Grounded in RAW, and every DM who’s watched this happen.)
So that’s the honest pile for a spell that spends most of its life being misunderstood. The throughline is simple: stop thinking of it as a morality detector and start thinking of it as a planar-and-undead radar with X-ray vision, and it goes from a punchline to a genuinely smart prepare. It will never out the evil king. It will absolutely tell you the evil king’s advisor is a devil. What’s the best thing your Detect Evil and Good ever caught, and be honest, did you cast it on a person expecting fireworks? Let me know in the comments below, and until next time, roll high and stay ridiculous.
