Base Class: Monk
Controlling the chaotic energies of magic inspires monks who seek to keep rogue mages in check. By trapping magical energies, they can starve a spellcaster of their strongest abilities and strike them down without their defenses.
Following this tradition allows a monk to find weak points in a spellcasters defenses and stop them from casting their spells. As wizards and sorcerers gain power, and generally taking that power too far as to subjugate others, monks of this tradition track down these foes and put them down to maintain the balance between arcane practitioners and those without magical talents.
Mage Hunter
When choosing this monastic tradition at 3rd level, you start training to use your ki in suppressing and stopping wild use of arcane and divine magic. By spending a ki point, you are able to cast Detect Magic without providing the material components.
If you hit a creature that has the ability to cast spells with at least two attacks in one turn, you may spend a ki point to force the creature to make a Wisdom saving throw or be unable to cast any spell of 1st-level or higher until the end of its next turn.
Magical Suppression
At 6th level, your ability to control the use of magic around you has expanded. By spending 3 ki points, you are able to cast Counterspell, Dispel Magic, and Nondetection at 3rd-level without providing material components.
Arcane Awareness
At 11th level, your dealings with magic have granted you the ability to sense incoming spells. When you are forced to make a saving throw due to a spell, you do so with advantage.
Archmage Hunter
Also at 11th level, you have improved your ability to shut down a spellcaster. When using your Mage Hunter feature, you are only required to land one attack against a target instead of two on a turn.
Spell Reflection
At 17th level, when you are the target of a spell that is 6th level or lower, you can use your reaction to attempt to deflect the spell. Make a Wisdom saving throw against the caster's spell DC.
On a success, you may spend 4 ki points to avoid the spell's effects and reflect the spell back at the caster. If the spell is a melee or ranged attack, make a spell attack using your Wisdom modifier and proficiency bonus. If the spell requires a saving throw, the target makes a Wisdom saving throw against your ki save DC.
On a failure, the spell targeting you is cast as normal.
Overall I think this hammers a bit too much on improving the monk's saving throws against spell, which are already some of the best in the game. To explain, monks already gain proficiency in all saving throws as well as the option to reroll any saving throw at the cost of 1 ki point via their Diamond Soul feature. To a smaller extent they can also gain advantage on Dexterity saving throws for one round as a bonus action at the cost of 1 ki point via Patient Defense and they take reduced damage on a large number of Dexterity saving throws against spells via their Evasion feature. Allowing monks to also have advantage on all saving throws against spells means a monk would have to fail the saving throw for a spell 4 times in order for it to affect them. For spells of 6th level or lower, the number of failed saves needed can be pushed as high as 6 (2 of which will be Wisdom saves) before the monk is affected by the spell and at a cost of only 2 ki points when they do fail them all (the cost to succeed will range from 1-5 depending on which saving throw is the first to make the save).
As for alternative ideas, instead of abilities that make monks even harder to hit with spells, I would like to see abilities that give monks benefits after they're successful in avoiding a spell. For instance, if the monk succeeds on a saving throw for a spell, they could either gain temporary hit points or gain some boost to their damage for their next attack or round.
I don't think it's absurd as it requires a Wisdom save and most spellcasting classes are able to add their proficiency bonus to this. Plus you need to get into the face of a mage to do that which is most often more difficult to pull off in practice.
Great subclass all in all. I believe I'll add it to my home campaign if that's alright with you?
I like the idea, but Mage hunter is incredibly powerful. Especially its upgraded version at 17th level. Monks are extremely accurate, and completely turning off all spells except cantrips for a whole turn is a little absurd. I would consider increasing the Ki point cost. Maybe instead of killing ALL spells for a turn, you can make Mage Hunter remove spell slots or innate casting uses from the creature.
Perhaps within Arcane Awareness, grant resistance against the damage of spells, similar to the Abjuration wizard's 14th level ability.
I love the monk character, this looks pretty solid! I'm going to look closely at this later on but seems like a very cool subclass both conceptwise and statwise!
Good point. I'm not too familiar with Monk ki costs, but that makes sense.
Increasing the ki point cost for Mage Hunter to 2 would be too much. As it is at 3rd level, you have to land two attacks, spend a ki, and then they have to fail a wisdom save to then not be able to cast spells. Monks already have a lot available to spend ki on and once they reach 5th level, why use this instead of stunning strike for only 1 ki point? Only way to make an increased ki cost make sense would be to eliminate the save and have it take effect after spending ki points.
Very interesting concept, hadn't thought of a mage hunting monk. Only thing I can say is maybe increase the ki point cost for Mage Hunter to 2? It seems a little to powerful for just 3rd level, but not by too much (since they would only have a limited amount of ki at 3rd level anyways).