Muggles' Guide to Harry Potter/Magic/Heliopath

Overview
Heliopaths, a magical creature apparently springing entirely out of the mind of Xeno Lovegood, are supposedly "spirits of fire", giant flaming creatures.

Extended Description
In Harry Potter and the Order of the Phoenix, during the initial meeting of the Defence Association in the Hog's Head, Luna says that Cornelius Fudge has an army of Heliopaths, telling Neville that they are spirits of fire, "great flaming creatures that gallop over the ground burning everything in front of them". Hermione states that they do not exist; Luna then angrily counters this by saying that there are plenty of eyewitness accounts of them. The incipient argument is only broken up when Ginny imitates Professor Umbridge.

Analysis
It is interesting to note Hermione's anger at this invention. Hermione, as we've seen, is somewhat hidebound, believing what she is told by "authority," whether that is teachers or books, and finds Luna's belief in this, and other apparently nonsensical creatures, aggravating. Curiously, this seems to be the last time in the series that one of Luna's invented creatures angers Hermione; after this, she seems wryly amused rather than upset at Luna's beliefs. No explanation is visible for this, but we can speculate that the abuse of authority she sees in Umbridge weakens Hermione's faith in authority in general. Alternately, of course, it may be simply that Hermione, maturing, sees much less in the world as being pure black or white, and becoming more accepting of unusual viewpoints.