British villains with "a tenuous grasp on reason", The Insaniacs are a collection of individuals whose motivations range from destructive nilhilism to a desire to spread chaos.  Each of them is mentally unstable to one degree or another and it is almost impossible to predict their actions.  They usually terrorize Great Britain and the Republic of Ireland and are seldom seen outside these countries, except for perhaps an extreme exception or two.

The Insaniacs do not seem to have any particular leader but seem to come to some sort of consensus.
 
 

Mad Janet: Apparently fourteen or so years old, Mad Janet is a sorceress of some talent, especially for her age.  She is able to cast a variety of destructive spells.  Her only limitation seems to be that her most effective casting must be through the medium of a wand.  The wands are made of different sorts of wood, each one giving her different abilities. She has been able to employ spells without them, but they are either more difficult to cast and/or far less potent.
Luna: An acrobat and contortionist, Luna seems utterly immune to pain.  That, or she does not mind it much at all.  She seems to have prenantural strength, possibly born of madness.  Her temperament is rather unstable, her mood swinging from manic to enraged in unexpected moments.
Samhain: No one is precisely sure what Samhain is.  He may be a simple fire elemental or he may be something much darker, more powerful.  He is brought into being by employing a carved pumpkin and a spell cast by Mad Janet.  When formed, Samhain likes to burn things....and people.  He has control over fire and is very strong, fast and tough.  Samhain's time is brief.  When his pumpkin head rots or is destroyed he must soon return from whence he came.