Muggles' Guide to Harry Potter/Magic/Umgubular Slashkilter

Overview
As it is only ever mentioned by Luna Lovegood, we must conclude that the never-described Umgubular Slashkilter springs from the fertile imagination of Xenophilius Lovegood.

Extended Description
During the first meeting of Dumbledore's Army in the Room of Requirement, in Harry Potter and the Order of the Phoenix, Luna says that her father is very supportive of anti-Ministry action, in part because of Cornelius Fudge's Umgubular Slashkilter. When Cho Chang opens her mouth to ask what it is, Harry tells her, "Don't ask", causing her to giggle.

Analysis
The only information we have about this creature is Luna's reporting Xenophilius' dislike of the Minister for Magic possessing one. This seems to imply that it is dangerous in some way.

Questions

 * 1) If this creature does indeed exist, why do you think it is not included on the Hogwarts syllabus?