Anti-Apparition (Anti-Disapparition Jinx)
Prevents someone from Apparating. (Apparating: Advanced spell used by fully trained witches and wizards to disappear from one place and appear almost instantly somewhere else. A person who uses this spell is referred to as an Apparator.)
--Used: Placed around the entire building and surrounding ground.
Caterwauling Charm
When an unauthorized person enters the target area while the effect is running, a caterwauling noise will be set off.
--Used: Same area as Anti-Apparition.
Cave Inimicum
Defensive spell to keep enemies away.
--Used: "Enemies" in this case are those who have not been specifically included in the spell.
Disillusionment Charm
A charm which hides the true, magical nature of something.
--Used: Merely used to hide the magic used on the prison so it looks completely normal.
Fidelius Charm
An immensely complex spell involving the magical concealment of a secret inside a single, living soul. The information is hidden inside the chosen person, or Secret-Keeper, and is henceforth impossible to find -- unless, of course, the Secret-Keeper chooses to divulge it.
--Used: Sirius is the Secret-Keeper for the Blackgate Penitentiary and is therefore the only one who can give away their location. If he dies then everyone he's told becomes the Secret-Keeper.
Repello Muggletum (Muggle-Repelling Charm)
Keeps non-magic users away from the target place or object.
--Used: This confuses anyone who wanders too close to the building, often under the impression that they've some other task to accomplish.
Stealth Sensoring Spells
Spells to detect anyone sneaking past them. Can be placed on physical objects such as doors.
--Used: A precaution for those who might try to enter or leave, placed on all doors, windows and any exits leading out.
Unplottable
A magical effect on a place; makes it impossible to plot its location on a map.
--Used: Once this goes up the prison will not be on any map.