Spell

A spell is an act of magic: a sequence of thoughts, words, and actions by which a practitioner channels magical energy to produce a change in the world.

Curses
Curses, such as malocchio, entropy curse, and the death curse are spells intended to do harm. They need some means of directing the magic at a target; body parts like hair, nail-clippings, fresh blood work best. To make a curse long-lasting, it needs to be anchored to an object or a blood relation.

Really strong curses require three people to cast the spell: one to gather the energy, one to shape it, one to aim it.

Props and tools
Though spells are mental constructs, most magical practitioners use various physical objects in casting them; many of them can get extremely complex and difficult to cast properly. The use of props reduces the amount of required mental effort.

A long-duration spell needs to be anchored to either objects, such as Harry Dresden's blasting rod, or people, in which case they need to be blood relatives to either the caster or the target. The Bloodline curse is such a case.

Circles of power are one of the basic tools of magic. An empowered circle creates a barrier that magical forces and beings of the Nevernever cannot cross, preventing magical interference from the outside. Circles can also be used to contain supernatural beings or keep them out. Setting up circles, gathering energy, and aligning forces can be time-consuming.

Names anchor thaumaturgical links to the being bearing them. Correct pronunciation is essential, and it is necessary that the name is given from the Name's bearer. Thaumaturgical links can also be created by enchanting a piece of the target; for human beings, hair strands, nail clippings, or fresh blood are excellent choices and can be used to aim a thaumaturgic spell at the person they were taken from.

Mirrors can be used as gateways by many things, such as Fetches, which is the reason Dresden doesn't keep any in his home.

Foci are magically prepared objects used to direct and execute spells. Common examples are staves, blasting rods, Pentagrams and pentacles.

Homunculi are objects used to temporarily host a spirit incapable of manifesting a physical form of its own. Some practitioners use fresh corpses, Dresden uses a Cabbage Patch doll as a vessel for Ulsharavas.

Cats are magic-friendly, and can move back and forth across magic boundaries, like circles without disturbing them. Cats can also see ghosts and spirits.

Blood has a kind of power; a practitioner can use blood to track the person who spilled it. Once it dries, or is excessively diluted, it's harder, if not impossible, to use. Different amounts of blood are needed according to the efficiency and skill of the magic user and how much energy the spell requires.