School of Nihilimancy

Most mages channel their magic from the Plane of Arcanum also known as the Eldritch Arcana, but there are those who are more interested in the dark temptations of the Void. Study of the void usually ends in disaster and destruction of the mage who studies it; However, there have been some cases in which the art of Nihilimancy was born.
Those who study in this school of magic are often seeking a way to bypass certain restrictions of spells, and to alter their properties. With the strange and disruptive nature of the void, this has made many mages' dreams a reality.

Void Channeler

Instead of focusing time on copying spells, a Nihilimancer learns how to harness void energy and channels it as needed. When casting a spell that deals damage, you may choose to change its damage type to: Cold, Force, Lightning, or Necrotic.

Dread Word

At 2nd level, you know the Dark Speech, and can utter its foul incantations to disrupt the spell-casting of others. As a reaction, when a creature is casting a spell, you speak a phrase of the Dark Speech and delay their casting by 1 turn. The caster must then use their action on their next turn to finish and release the spell, or take 1d6 necrotic damage per level of the spell the target attempted to cast.

Siphon Arcana

Beginning at 6th level when you cast counterspell or dispel magic on an object or creature that is casting a spell or affected by a spell, you can siphon the arcane energies from that object or creature. You add the spell you countered or dispelled to your prepared spells until you finish a long rest, you cast the spell, or you use this feature again, replacing the absorbed spell with the new one.

Eldritch Mind

Beginning at 10th level, you are allowed to concentrate on two spells at a time for a number of rounds equal to your Intelligence modifier. Losing concentration for either of the spells ends the concentration for both.

Spell Breaker

Starting at 14th level, you have the ability to bring forth a fraction of the Void to your location. This clashes with arcane and divine energies, disjunctioning them and siphoning their power for your own. Make an Intelligence ability check against the Disjunction DC (DC = 10 + Spell Level active on target creature).
For each creature within 30 feet of you with an active spell that the ability check succeeds on, that effect is dispelled and you gain the following benefits for up to 1 minute or until you lose concentration (as if concentrating on a spell):

• Bonus to spell save DC and saving throws against spells and other magical effects increase by 1 for each effect dispelled (maximum of +3)
• Gain a number of temporary hit points equal to the total number of spell levels of effects dispelled.

Once this ability is used, it can't be used again until you finish a long rest.