I'm making another new character and this one I'm not sure on the class to pick.

So this character was very young (12) and really annoyed a Wizard - probably by trying to steal his spellbook or something. In return he Plane Shifted her to the Feywild where she wandered for a while before getting killed. She was resurrected and returned to the material plane by an archfey. Now she wants revenge - particularly against the Wizard who got her killed - but in general to anyone capable of doing that. Essentially she wants to become a mage killer.

I think I'm leaning towards more martial classes (like Shadow Monk or Inquisitive Rogue) but I'm not against a magic class (fight fire with fire) and I'm sure I'm overlooking some really good options. My only restriction is definitely not a Sorcerer. I don't have any precedence for a Sorcerous origin in the backstory.

I also haven't decided on a race for this character yet so if that factors into your decision feel free to suggest one. Thanks.

School of Abjuration -- pretty much everything you get makes you better against other spellcasters!

You said you didn't have a precedent for being a sorcerer, but going to the feywild could be a precedent for wild magic sorcerers.

You could also do archfey warlock. Why did the fey bring you back to life?

We had an Aarakocra Rogue that ended up going Arcane Trickster to get a Familiar.  Triggering his own Sneak Attacks gave him a ton of extra damage dice, and the innate Flight from being a bird person combined with Rogue's movement enhancements gave him free range to do pretty much whatever he wanted in combat.  Into and out of combat at will, stay back and fire arrows for a while or move in and fillet someone.

I am also interested...  why did the Archfey resurrect you??  And would that experience itself not be a possible Sorcerous Origin itself for Wild Magic?

 I like the idea of a Pact of the Blade Archfey Warlock, looks like it will go good with the Mage Slayer feat.  Then once you can take a level or two of Abjurer just for good measure.

Quote from DxJxC >>

You said you didn't have a precedent for being a sorcerer, but going to the feywild could be a precedent for wild magic sorcerers.

Quote from drag0n_77 >>

And would that experience itself not be a possible Sorcerous Origin itself for Wild Magic?

That's true she could be a Wild Magic Sorcerer - I always forget that subclass. I never consider it because the randomness really puts me off - it's just not a subclass I think I'll ever play.

As for why she was resurrected - I really don't know. I like to leave things like that open in a backstory for the DM to decide. Basically if my character doesn't know it - it doesn't make it onto the backstory. I imagine it would be either idle curiosity or pity depending on their mood at the time - though really for an Archfey it could be any number of reasons.

Anyway - thank you for the suggestions. I'll give them all a look.

Shadow Monks with Mage Slayer feat are pretty good. Their ability to sneak up on mages, stun them, cast silence, teleport and overwhelm with melee attacks (most mages are typically disadvantaged at close range). Plus with mage slayer you can use reactions to interrupt their spellcasting and you can easily stop them getting away if you can also get Sentinel - either you're locking them down with sentinel if they try to move or you can instead prevent their spellcasting. They're not usually built for melee so they are less likely to have high Con - making stunning strike great. You can reserve ki for stuns more than for flurries because their health is more likely to be lower than melee-focused enemies.  With sentinel and stuns you can keep them in Silence preventing quite a lot of their spellcasting, and if they do get to move out - well, your monk speed and shadowporting easily lets you out-maneuver them. Plus their bigger blasty spells are quite commonly Dex, and you have evasion. 

As has already been suggested, Rangers are good too. Basically any class with Wisdom as an important stat is good because some of the more "oh crap!" spells are control spells which target wisdom - your build, no matter what it is, could be easily shut down into useless with a simple Suggestion, Hold Person or worse still a Dominate Person! But a fireball can be more easily contended with. So you are going to need wisdom and a class that will want you to put into wisdom or have wisdom saving throw proficiency. Since both rangers and monks use wisdom they're good choices for these, offer more than sufficient damage output and have extras that can help you out against casters. They're also both good at using Dex for weapons - so even if the sneakier wizard tries a Ray of Enfeeblement it will mean nothing to you.  

I would recommend taking a look at the spells available for wizards and sorcerers (the more common mages) and think "what would be the best way to defend against that spell?" - Having a balance of defenses against these spells will be very useful - and this isn't metagaming: your character dedicated themselves to hunting mages, so, clearly, they'll have made sure they know what they're up against.

Hope these suggestions help.

I like the monk + mage Slayer since you get a ton of hits to interrupt concentration spells.

I agree. Monk/mage slayer definitely a neat concept.

Yea Shadow Monk with Mage Slayer does seem like a very good option. Ability to cast silence and has 3-4 attacks each triggering a concentration check at disadvantage with Mage Slayer - and getting the 'within 5 ft' bonuses from Mage Slayer too that a Ranger or spellcaster wouldn't. Then again Ranger sounds really cool too and like Sillvva suggested the Monster Slayer seems written to be a witch hunter and mage killer.

Difficult to choose.

I ran a Kensai monk with mage slayer.  At high levels, having advantage with all saves, stuns, extra damage dice I was a nightmare for the DM.

But i do like the Shadow kit idea though. Would love to try it out.

I love the concept of the mage slayer and what I would want to play is not as optimized as what has been suggested. I like the idea of a tavern brawler grappler that throws the mage around like hulk does with loki. 

Consider the War Domain Cleric. Fun spells like Silence, Antimagic Field, etc. With a high AC, you can walk straight up to the wizard and slap them no problem.

Quote from Waltahr >>

Consider the War Domain Cleric. Fun spells like Silence, Antimagic Field, etc. With a high AC, you can walk straight up to the wizard and slap them no problem.

 Cleric also already has WIS and CHA saves. Just get shield master and you can shrug off almost any wizards spell.

Shadow Monk is one of my favorite anti-mage build. Way of the Four Elements also has some niche applications there due to Fist of Unbroken Air letting you apply guaranteed damage without having to see the creature and it can't be counterspelled, so it's a great way to force concentration saves against Greater Invisibility. It'll also bypass Shield and Mirror Image, which are two of the best defensive spells.

Oath of the Ancients Paladin is also a strong contender thanks to the combination of Aura of Protection and Aura of Warding making most forms of magic relatively ineffective. Like DxJxC said, Shield Master is handy for the pseudo-Evasion it grants, which synergizes well with Aura of Protection's saving throw bonus. Branding Smite and Banishing Smite both work with bows; the former will negate invisibility and the latter will completely stop an injured spellcaster's concentration if they drop to 50 HP and get banished to a demiplane.

The War Magic tradition for wizards is also naturally geared towards fighting other casters.

Eldritch Knights can use Indomitable and Shield/Absorb Elements to protect themselves against spellcasting and can shut down enemies with Action Surge for burst damage and forcing concentration saves, as well as Eldritch Strike and save-or-suck spells like Blindness/Deafness or Slow. Gotta work fast though, since once Action Surge and Indomitable are spent you're losing your biggest advantages.

Wizards are pretty versatile, so they can target any one of your saving throws and devastate, but the scariest spells have to do with Wisdom and Charisma saves, you know the spells that take over your mind. This would be my primary thought with building a character. 

First, go High Elf, immunity to sleep spells and the bonus to dexterity already benefits you against some wizard spells. On top of that, they get a free cantrip (infestation is my choice for concentration interruption on wizard spells). 

For class, I like going with Ranger here (with the Archery style), this gives you bonuses against a favored enemy (choose whatever race the wizard is) and gives you range to deal with him. This also buffs your Dexterity and Wisdom saves, which is good for avoiding getting charmed (plus you have advantage from Fey Ancestry). 

For lore/story wise I would go Horizon Walker mainly because it is all about moving through the planes. That's just my 2 cents.

Yeah. With heavy armor and high STR, you can dump dex and just go Shield Master.

A multi-class into this after a level of fighter gives advantage on Con saves too if I'm not mistaken. That could also be a decent replacement for the War Mage feat if we want to play with keeping a shield hand free.

More levels can get us to Eldritch Fighter, Samurai, Battle Master, or Cavelier, all of which have fantastic options for locking down the target mage with multiattack and opportunity attacks.

rouge assassin/monster slayer with the mage slayer feat, with that tiny HP pool, one good sneak attack and they're dead.

Eldritch Knight, or at least that is what I have mine setup to do. Counterspell, misty step, mage slayer feat, great weapon master... Get up close and just wreck casters.