Spellcasting is one of the common abilities of Witches, if not their most used ability, along with potion-making. It is used to produce change on realities and induce magical effects of various sorts.
As mentioned by Wendy Beauchamp, spells already exist and Witches must use them in their true original form for it to work. Tweaking on the contrary often brings disastrous complications to the effect intended in the first place. However, some talented Witches were said to be able to craft spells of their own - Ingrid, in her previous lifetimes, was one of those gifted Witches.
There are various kinds of spells, such as protection spells, elemental spells, creation spells or spells of dark magic. Spells can be chanted by one or several Witches.