A practical primer on invisibility, group concealment, misdirected attention, and the limits of magic that changes perception without changing physical reality.
Illusion changes what a mind or sensing system notices and how it interprets what reaches it.
It can bend light, soften a recognizable outline, place an image where nothing stands, or persuade attention to pass over something that remains physically present. The school works through perception. It does not remove matter from the world.
An invisible person still has weight. Their feet still disturb dust and water. They can make noise, carry a scent, open a door, cast a shadow under the wrong light, and collide with whatever occupies the space ahead of them. Anyone who forgets this has confused being difficult to notice with being absent.
Invisibility
The common invisibility working folds a cloak around one person. To an enemy seeking a new target, the wearer becomes difficult to select and follow. This is most useful before the enemy commits to an attack.
The cloak does not stop an arrow already in flight. It does not remove the wearer from a spreading fire, a collapsing floor, a cloud of poison, or any other danger that fills an area. A creature sweeping the room with a pole may strike an invisible person without ever seeing them.
Hostile action breaks an ordinary cloak. The caster cannot begin an attack while remaining hidden behind it. Starting a direct interaction also reveals the wearer: opening a chest, working a mechanism, helping another person with their equipment, or handling an object closely enough to make the unseen motion obvious.
Taking an injury that reaches the body breaks the cloak as well. Blood, displaced cloth, a sudden cry, and the shock to the working all reveal what the illusion was hiding.
The safest use is movement with a purpose. Leave a threatened position. Cross a watched opening. Reach a wounded ally. Break an enemy's clear choice of target. Invisibility is not a reason to stand in danger and hope danger forgets where it was aimed.
Mass Invisibility
Mass Invisibility lays a separate cloak over each nearby ally the caster can include when the spell is formed. The group does not become one shared invisible object. Each person carries and can break their own cloak.
One ally attacking does not reveal everyone. One ally being struck does not tear the spell from the rest. This makes the working useful for a scattered retreat or a coordinated approach, but it also demands discipline. A single impatient fighter can reveal themselves early and draw danger across the path of companions who are still concealed.
The working also creates a field of shifting false positions around the group. Even when an enemy finds a target, the displaced outline makes a clean strike less likely. This protection is separate from the individual cloaks. Concealment prevents clear selection; the shifting field makes attacks less accurate after selection.
Do not assume that a group cloak makes a group quiet. Armor still knocks against armor. Boots still strike the ground. Spoken instructions still carry. Parties that need silence must provide it through training and equipment rather than asking a visual working to do another craft's job.
Duration and control
Every illusion has a duration. The caster must maintain a convincing relation among light, movement, distance, and the expectations of whoever is watching. Experience extends that control, but no amount of confidence makes a temporary working permanent.
Lasting Glamour disciplines keep timed illusions stable for longer. Quiet Weave reduces the time needed to form them. These are different skills. A quickly cast cloak may still be brief, and a long-lasting cloak may still take too long to save someone already under attack.
Bent Light strengthens the false positions surrounding an illusionist and makes attacks against them less accurate. Misdirected Blame goes further. When an enemy misses because it struck an illusion instead of the person, the enemy may lose some of its certainty about whom it was pursuing. The technique reduces attention that already exists; it does not make every witness forget the caster.
Advanced practitioners sometimes learn Unbroken Image, which can hold a cloak through the first direct injury that would normally reveal it. The body still takes the harm. Only the image survives.
Subtle Weave can conceal the start of one non-hostile Illusion working while a cloak is active. It does not permit a hidden attack. Afterimage leaves a brief false motion behind when invisibility ends, giving the revealed caster a final chance to evade.
These techniques improve particular failures. None removes every limitation at once.
Observers and instruments
Different observers notice different evidence. One creature follows color, another movement, another heat, vibration, scent, or changes in air pressure. A machine may ignore a face yet respond to a broken beam, an added weight, or an unexpected sound.
Mirrors and lenses can expose an illusion that was shaped for one angle. Several observers spread around a room force the caster to satisfy several viewpoints. Rain, dust, smoke, shallow water, loose cloth, and strong backlighting reveal motion the cloak does not erase.
There is no single perfect test for all illusions. A careful observer compares several kinds of evidence and avoids assuming that sight is the whole world.
Illusion serves scouts, rescuers, performers, hunters, investigators, and travelers trying to escape a fight they cannot win. It can also be used to frighten, deceive, and ambush. The school does not decide the purpose. It only changes what can be perceived long enough for someone to act.
