Mage-Hunter Domain

For some, magic is a blessing. A wondrous power capable of truly wonderful things. Magic, however, can be volatile and dangerous. From Necromancy which raises corpses from the grave, to Sorcerers unable or unwilling to control the massive surges of power within their blood. Whatever the intent behind it, all magic has the potential to cause terrible damage. Some clerical orders have realized this long ago, and as such have taken steps to combat these powers. These feared Clerics are known by many names: Templar, Legates, Mage Hunters. All serve a similar purpose: To hunt down and destroy practitioners of the Arcane. Some are noble, and hunt only those who have done terrible things, keeping those who would exploit such power in check. Others follow deities who wish to see the scourge of the arcane to be wiped from existence.

Bonus Proficiency

When you choose this domain at 1st Level, you gain proficiency with all Martial Weapons.

Expanded Spell List

Each domain has a list of spells-it's domain spells- that you gain at the cleric levels noted in the domain description. Once you gain a domain spell, you always have it prepared, and it doesn't count against the number of spells you can prepare for that day. If you have a domain spell that doesn't appear on the cleric spell list, the spell is nonetheless a cleric spell for you.

1st: Detect Magic, Hunter's Mark

3rd: Hold Person, Locate Object

5th: Counterspell, Dispel Magic

7th: Otiluke's Resilient Sphere, Freedom of Movement

9th: Scrying, Dispel Evil and Good

Channel Divinity: Siphoning Strike

Starting at 2nd level, you can use your Channel Divinity to drain magic users of their arcane power. After you have successfully hit with a melee weapon attack, but before your roll damage, you may expend one use of your channel divinity. The target must make a save using their spellcasting ability. If the target had multiple attributes for spellcasting, they may choose which save to use. The DC of this check is 10 + the damage dealt by your weapon attack. Any additional damage, such as from a spell which deals bonus damage on weapon strikes is not counted towards the DC of this save. If the target fails, the target loses a single spell slot of their choosing. If the target fails by 5 or more, you may choose which spell slot is drained. This ability may be used on any creature that can cast spells. This ability has no effect if the target cannot cast spells, or if all the target's spell slots have been expended.

Disruptive strikes

At 6th level, you have learned specific strikes which will disrupt a spellcaster's ability to concentrate. Any concentration checks you force a spellcaster to make are at disadvantage.

Improved Siphoning Strike

Starting at 8th level, after you have used your Siphoning Strike ability, and your target has been drained of a spell slot, you may restore an expended spell slot equal to half the level of the spell that was drained, minimum 1st level. You may not exceed the maximum number of spell slots you are allowed to have based on your character level. 

Channel Divinity: Null Shield

Starting at 17th level, you may use your Channel Divinity to become immune to the forces of magic or to suppress any on-going effects of magic already cast upon you.  As a standard action you may expend a single use of Channel Divinity. You may do this even while incapacitated. During the next round no magic, good or bad, may affect you until the end of your next turn. Any spells with lingering effects, such as a slow spell, is suppressed, though these effects return at the end of your next turn. While under the effect of the Null Shield, you may not cast spells but may move, attack, use items and make saving throws. You may make saves against suppressed effects as normal. You cannot choose which spells affect you and which are suppressed, all are nullified for duration of the round. Summoned creatures can still attack you and indirect magic may still affect you, such as the illusion of illusory terrain. However any magical damage, such as the blast from a fireball, or spells which directly target you are nullified.