Twisted Barricade

You pull forth a portion of your own hateful or loathsome soul which bursts from your body as thick twisted branches that distorts the weave of magic. For the duration you cannot be affected by spells of 3rd level or lower unless you want to be. The hit points lost to this spell can only be regained on a long rest.

Sacrifice. You may instead cast this spell for 1 hit dice per spell level, even if you have no spell slots remaining. This spell still requires the material component if any to be cast. 

At higher levels. When you cast this spell using a spell slot of 5th level or higher, the spells that cannot affect you increases by 1 for each slot level above 4th. The amount of hit points you sacrifice also increases by 5 for each spell level above 4th.

Dark sorcery created by the Dread Witch of Oolacile. Most if not all the spells she created were motivated by fear. To inflict pain on one's self for protection from others can be seen as insane, until it saves your life.