The Runespoor is a magical three-headed snake commonly reaching a length of 6 – 7 feet and colored livid orange with black banding. It is native to Burkina Faso, where several forests are designated as preserves for its sole use. The runespoor is unique among known magical beasts for producing its eggs through its mouths (FB).
Runespoors rarely live to a great age, as each head contains an independent brain serving a different purpose, and they tend to attack each other. The right head is the planner, the middle head is the dreamer, and the left head is the critic. The planner decides where the runespoor goes and what it will do next, although the dreamer’s visions often lead to a runespoor remaining stationary for days, lost in its imaginings. The critic, the fangs of which are extremely venomous, hisses continually (and irritably), evaluating the efforts of the planner and the dreamer. Often, the other two heads will gang up on the critic and bite it off; two-headed runespoors are not uncommon.
The runespoor was once a favorite pet of Dark wizards, mostly because of its intimidating appearance. A flourishing black market in runespoor eggs and in the serpents themselves has existed for centuries (FB).
Newt Scamander carried two Runespoors in his suitcase in December 1926: an apparently normal-sized individual whose right head was wearing a protective cone, and an unusually gigantic specimen (FWT)
A Runespoor appears in the background of one of the deleted scenes where Newt is showing Jacob the interior of his suitcase. (FWT)
"rune" one of the alternate meanings of this word in English is 'an incantation, a charm, esp. one denoted by magic or cryptic signs; a magic word' [NSOED]