Bargrim

At the heart of the enigmatic and dangerous school of void magic lies void speech. The glyphs and spoken words of the void are the essence of oblivion given form.

Wherever anyone utters void speech, no matter how well-meaning, darkness follows. Things from beyond hear the call and can follow its echo into existence. With sufficient study and preparation, a speaker into the void can protect him or herself from the brunt of the horrors that arise and even turn deadly manifestations against foes. No amount of caution in using void speech and magic, however, can completely shield a practitioner from its corrupting nature. The void will have its due. 

Proficiency in Void Speech: Under normal circumstances (or what passes for normal where void speech is concerned), only wizards can learn void magic. The following two  feats make it possible for any character to channel the power of void speech in a limited way. At the GM’s discretion, a character may be able to learn void magic spells without finding them in written form, as if he or she was a void savant.

Void Channeler (Feat):  As an action, you can speak aloud a word or short phrase in void speech. One creature of your choice within 10 feet that can hear you must succeed on a Wisdom saving throw against this magic (DC 8 + your proficiency bonus + your Charisma modifier) or be frightened of you for 1 minute. A frightened creature can repeat the saving throw at the end of its turn, ending the effect on itself on a success. Other creatures who can hear you suffer minor reactions to the void speech such as spontaneous nosebleeds,  headaches, bits of hair falling out, and other unsettling effects. The first time you use this ability, you suffer no adverse effect. If you use it again before completing a short or long rest, you take 1d4 necrotic damage. Each additional time you use it before finishing a rest, the necrotic damage increases by 1d4.

Void Scribe (Feat): As an action, you can use a writing medium to inscribe a magical void glyph on an unattended object within reach. As long as the glyph remains intact, the object is vulnerable to necrotic damage and it takes 1d6 necrotic damage at the end of your turn. For the glyph to remain intact, you must concentrate on it as if  concentrating on a spell. In addition to the normal demands of concentration, you must also make a successful DC 10 Constitution saving throw at the start of your turn or the glyph crumbles away and ceases to function.