The displacer beast is an evil feline monster created for Dungeons & Dragons in 1975 and included in every edition of the game since. It is a six-legged, black, panther-like cat with a pair of tentacles growing from its shoulders. Its name comes from its innate “displacement”: it magically bends light so that it appears to be a short distance from where it really is.
It first appeared in the 1975 supplement Greyhawk as “a puma-like creature with six legs and a pair of tentacles which grow from its shoulders,” and in the first Monster Manual (1977) as a beast that always appears to be three feet from its actual position. The concept was borrowed from the coeurl, a feline creature in A. E. van Vogt’s 1939 science fiction story “Black Destroyer.”
For the third edition, Wizards of the Coast classed it as “Product Identity” — an original D&D creation — and kept it out of the Open Game License. It also appears in the film Dungeons & Dragons: Honor Among Thieves.