Stop! This is the Magic Police!

[Emay Ecks]

There's good odds I'm going to be dming a new campaign for 3-4 people. It's going to be an urban campaign in a high fantasy setting with the premise that the party is a special police task force dealing with magic-related crime. I got really excited thinking of all the fun crimes I can have people committing using magic. Before getting started, I wanted to get some character ideas to recommend to players (one of them is new) and ideas for fun villains and criminals I can have the party investigate and stop.

If you were designing a magic police investigator, what class/spells/abilities would you use?

If you were designing magic criminals, what crimes would they be committing and how would they be doing it?

Thank you very much for your help!

Some ideas I had:
-Ring of druid smugglers carrying large amounts of contraband, turning into rats, and moving it in or out of a city.
-A Mask of Many faces warlock who robs stores with charm person, friends (the spell), suggestion, and an invisible imp
-A magical serial killer who uses modify memory to make nearby witnesses think they committed the murder (likely by convincing them it was an accident or self-defense)
-Someone using Nystul's magic aura to accuse innocents of being vampires

[Easy_Lee]

For the investigator, Detect Magic and a solid Insight check would be a must. Bards would be ideally suited.

I imagine such a society would have a lot of laws specifically designed to keep magic users in check. Fabrication by itself would probably be an entire branch of law:

Fabricating money
Fabricating official seals and documents
Fabricating keys to peoples' houses without their permission
Fabricating counterfeit art, or counterfeit anything really
Using fabricate to out-compete other forms of labor

I can think of a lot of laws for fabricate.

[Mjolnirbear]

Divination spells, insight skill, zone of truth, or suggestion. Survival (tracking) and investigation. Ritual Casting for unlimited Detect Magic or a magical item to see magic.

Criminals would:
* use fake materials (conjuration)
* evade detection (nystrul'sagical aura)
* pose as individuals ("Tod can't have ordered the release, he was on an errand for Lord Pinochle!")
* fraud (why yes, here are my travel documents. And this is my valid receipt for these goods)
* dangerous magic (cast a fire spell on a ship, fail to contain your conjured beast)
* manipulators (did use magic to influence Lady Poncey's horse, magically compelled an agent of the law to release your manacles )
* mischief (did cause the sewers under Duke Stupidhead's mansion to back up by means of summoned elementals)
* irresponsibility (did recklessly Confuse your attacker and thus causing the death of one Seamus Beggarboy)

[JellyPooga]

Warlocks would make great investigators; Detect Magic at will, Devils Sight to pierce magical Darkness, Chain Pact for the perfect "eye in the sky", GOO patron for lots of investigator-y spells. Pact Magic refreshing on a Short Rest explains why the "cops" need so many coffee/doughnut breaks!

All you need is an appropriate Patron.

[Hadhfang]

Oh boy! This is a topic close to my heart as my current campaign setting has a magic police well established in it.

For the guys who bust in and stop rogue mages (your spells, weapons and tactics- or SWAT team hur hur)They tend to have the following spells :

Hold Person
Anti-Magic
Counterspell
Shield

Those are their bread and butter spells if they can cast and/or have magic items to cast them. If you have SCAG then lightning lure is a potential choice as well for pulling them closer for the arrest- criminal magic users aren't likely to be that strong 90% of the time. If you are using feats, Mage slayer is a must. These guys tend to be Eldritch Knight/Gish based- enough magic to get close to the enemy, but then a strong enough arm to clobber them when they're there.

For the investigators as others have said detect magic, Zone of truth for interrogation, and all the usual skills that go with making a solid investigator. Speak with dead could be very useful for getting a lead on murderers.

With regard to magic crime and criminals - You said that you want to have a high magic setting. If you have a magic police then it is possible you have magic items regulated. Different power levels (rarities) get different classes- A, B, C etc. So unlicensed magic items could be a big crime. On the topic of licenses too - My setting has all magic users licensed- so unlicensed practitioners in town could be another potential criminal activity - but I do appreciate that the paperwork aspect of heavy licensing may not be for everybody so your mileage there may vary.