Congratulations... you found the page where I give sneak peaks into my brainstorming. This is similar to how WotC have unearthed arcana, but these ideas are not ready to be playtested yet. I welcome all inputs to my ideas and any constructive criticism you may have to give.
Mage Bane:
Premise: There needs to be ways for martial classes to catch up with spell-slinging magic users. This feat should be sufficient to do this.
Prerequisites: Minimum level 5 character; must have the mage slayer feat.
Description: For whatever reason, you have become so proficient at combatting magic users that you have developed an affinity to anti-magic. This affinity seems to be a double-edged sword, like the one you cleave into the chest cavity of those pesky wizards.
Spells have difficulty landing on you; spell attacks have disadvantage against you, and you have advantage on saving throws caused by spells.
You have severed any possible link between you and the magical weave; if you had the spellcasting feature then you no longer have access to it. Magical items still function around you, but you cannot cast spells through an item.
You gain the ability to use an effect similar to Counterspell, you can use it a number of times equal to your proficiency bonus per day, recharge after a long rest. This ability is not considered a spell.
College of Disk Jockeying
Cupid's Irresistible Shuffle
Level 3 Spell
Description:
You play a song that causes your targets to do a trendy line dance. If they fail the a wisdom saving throw, then they are charmed, reduce their movement to 0, aka they are stuck in their 5ft square to do their dance. They may use their action to try to make the save again.