Witches are a type of monster in Undertale. Witches look half human and half animal, but are known to be completely monster. Witches are a strange race. Aside from their appearance, they are also not born from one another. They are instead born from trees. These trees only bare one witch at a time. The gender of a witch is usually female, but male witches (also known as warlocks) have a small possibility of being born. Once the witch of a tree dies, the soul returns to the tree makes a new witch. Because of this, witches are also infertile and usually grow up alone unless adopted. A tree that's cut will wilt away quickly, leaving a seed in its place. Seeds are often unable to be replanted since they are eaten by animals, and when the seed is eaten the soul shatters. There used to be plenty of witches, but that has since been changed. Witches began to be less and less common as the war between humans and monsters came about. Many witches were murdered by both monsters and humans as the division between races grew stronger.
Witches are alike to skeletons in the way they are named. Like skeletons are named after the font they use to talk with, witches can be named after their position, element, and/or hobby. Serana's name is used to describe a witch who loves music, Serana being a play on the word "serenade" which means "to sing," Aria being a music term that means a solo voice singing with an orchestra, and Jazett being a play on the word "jazz." Sometimes witches named after hobbies don't become invested in said hobby and get a name change as they grow older. Other times, witches aren't named until their magic type is discovered. Records that keep track of witch trees may show their expected magic type before their magic is fully developed.
Witches are usually in tone with nature, and thus have elemental powers. A witch often either inherits their ancestor's power or they are given a new power when reborn. There is a 50% chance of power change, and a 50% chance of power inheritance. Evil witches will willingly learn dark magic, whereas good witches wouldn't think of it due to possible soul corruption. A witch with a corrupted soul is often never fixed, even after one or more reincarnations. Whether good or bad, all witches also have the ability to transform into the animal that they are half of. For example, Serana could turn into a wolf if she so chose to.
All witches may have a familiar, which helps their magic become stronger and last longer. Once a witch dies, its familiar immediately becomes profusely ill and dies as well. Familiars come in all shapes and sizes and can usually levitate as well as shapeshift, usually choosing a single form that's suitable to stay in. Once a familiar has an owner, the familiar may also begin to pick up abilities from its owner, but may also have half the power. Exactly when a witch will get their familiar is unknown, but it's usually known as a day where something very important happens to them.