Evocation

From Thelemapedia

In Ceremonial Magic(k), Evocation or Evokation is the act of manifesting the abstract intelligence of an entity into a physical receptacle, such as a triangle, mirror, crystal ball, shard of quartz, bowl of standing water, or other implement designed for the reception of energies or influences. Usually, the entity is then skryed, or "seen without looking" by generally dulling the sensory organs, and interacted with by the magician via the skryer. The identity of the intelligence is verified by asking it to validate certain symbols, found appropriate to its domain, to be truly representative of itself. This is commonly performed through usage of Gematria.