Incorporeality allows one to pass through solid objects. Like a ghost, a person performing Incorporeality magic can hover and drift uncannily.

Concentration
You must concentrate to maintain incorporeality.

Holding One's Breath
You must hold your breath to maintain incorporeality.¹⁾²⁾

Managing the risk of 'Melding'
You must be careful not to cease being incorporeal while overlapping with solid matter. If you end your incorporeality while overlapping with a solid object, your body's matter can become melded with that object, causing injury.

Become Incorporeal
You may use an action to make your body incorporeal. You may end any incorporeality effects freely. To maintain incorporeality, you must hold your breath and concentrate. While incorporeal, all matter passes through your body, and gravity has no effect on your body. You can move slowly, up to 2 meters (or 5 feet) per turn in any direction, even against gravity, and you may also move through solid objects. Ending incorporeality (becoming corporeal) while your body intersects with a solid object is potentially lethal as it causes your body and that object to become melded together where they intersect - while you may free yourself from that object by becoming incorporeal again, doing so does not heal injuries caused by melding. Ceasing incorporeality while inside an atmosphere or submerged in liquid simply pushes that matter out of the way, causing a small 'pop' or 'whoosh' sound. If any effect would cause you to stop holding your breath or break concentration, you immediately cease to be incorporeal. While incorporeal, your body appears translucent, as if made from smoke or fog. Note that without the 'Clothed' perk, your clothes and objects you carry do not become incorporeal with you. Your senses work differently while incorporeal: Vision and hearing are dulled slightly, smell does not function at all, taste and touch may work once the 'Poltergeist' perk has been acquired. When you gain a rank in this ability, even the first rank, you may choose ONE (1) perk to enhance your ability.

Each time you gain ranks in Incorporeality, you may also gain your choice of one of the following perks:

Breathless
You no longer have to hold your breath to become incorporeal or maintain incorporeality.

Clothed
You may choose to have your clothes (armor and jewelry included) considered as part of your own body when you become incorporeal; doing so imposes no risk of melding with your clothes. Backpacks and carried objects do not count.³⁾

Ethereal Nature
You no longer need to concentrate to maintain incorporeality.

Fast Flight
Your movement speed while incorporeal increases to your normal movement speed while not incorporeal.

Invisibility
While incorporeal, you may choose to become entirely invisible. This invisibility can be foiled by such effects as true-sight, or being seen by other incorporeal beings.

Poltergeist
While incorporeal, you may choose to manipulate light objects as if you were not incorporeal. You may manipulate up to five kilograms (ten pounds) total weight of objects, as limited by your character's skill in manipulating those objects normally (For example, you cannot juggle objects using this perk unless you can also juggle without it). Doing so imposes no risk of melding with the object(s) being manipulated. You may take this perk multiple times. Doing so increases the total weight of objects that you may manipulate by five kilograms (or ten pounds) up to an amount appropriate for your character's strength and skill while not incorporeal - additionally, you may choose to have such objects become incorporeal while you manipulate them. If you lose control over an object made incorporeal by you, such as dropping it, or the object hitting another object after being thrown, it ceases to be incorporeal.

Possession
While incorporeal, you can attempt to gain control of another creature's body. To do so, you must occupy the same space as the creature and use an action to possess the creature. While in possession of the creature, you can control it as if the creature were your own body. The creature loses their turns to act while you maintain control (the possessed creature loses all actions and movement). While in possession of a creature, you have access to any ranked abilities and perks that they do. However, at the end of every turn that you hold possession over a creature, the creature may attempt to wrest back control of themselves. This initiates a round of spiritual battle. Domesticated animals generally do not attempt to wrest back control for a day; wild animals for one minute; sapient creatures such as humans may attempt to wrest back control as soon as they are allowed.

Spectral Stitching
Whenever you transition from corporeal to incorporeal, you may cure one light, physical injury to your body. You may take this perk up to three times, each time increasing the severity of injury you are allowed to cure when you transition to incorporeal. First time: One light, physical injury. Second time: One light or severe physical injury. Third time: One light, severe, or mortal physical injury. If you have the perk 'Clothed', you may repair your clothing to a degree appropriate to the severity of injury you can cure. If you have the perk 'Poltergeist', you may repair an item held to a degree appropriate to the severity of injury you can cure.

Vaporize
You may use a reaction instead of an action to become incorporeal.

Undeath
If you die, your ghost-form body separates from your corpse and becomes permanent, persisting after your body's death. I.e.: Your character is now a ghost, indefinitely. Since your body is dead, the requirements to maintain incorporeality are lifted - you no longer have to hold your breath or maintain concentration to maintain incorporeality.

1. First, The victim (the creature who is possessed) attempts to wrest back control over themselves.
2. Then the possessor bids an injury they are willing to take to maintain control.
3. If the possessor bids no injury, then the possessor is immediately expelled from the possessed creature's body, and the creature regains control over their body.
4. If the possessor bids an injury, the creature may then choose to take no injury or match the bid.
5. If the possessed creature does not take an injury, the possessor maintains control and takes their bidded injury.
6. If the possessed creature chooses to match the bid, then both creatures take the bidded injury. The creature then may choose to either expel your incorporeal body, or hold it prisoner in their body until the end of their next turn, at which point the former possessor may attempt to wrest back control in another spiritual battle.

The 'Clothed' perk is subject to interpretation. The original intent is that backpacks and stuff therein, or weapons or tools carried, don't count as clothing. This is meant to prevent ghostly characters from rendering other characters specializing in thieving or assassination from feeling redundant or underpowered. The 'Poltergeist' perk was written to compensate for the possible power difference.

The 'Poltergeist' perk is very powerful when upgraded, as it potentially allows such characters to make an object corporeal when it intersects with another creature or object, causing them to meld together. When this happens between two objects, they form a weld that is as secure as the materials they are made from - good for grappling hooks, securing doors, building bridges, etc. When this happens between a manipulated object and another creature, perhaps between the ghostly player's sword and an enemy, that object can potentially form a lethal weld between itself and the enemy. It is important to note, however, that this causes the object and the creature welded to it to be considered a single object, and may cause the welded objects to exceed the weight limit of the Poltergeist perk. Retrieving the object intact may be impossible without magic, as its substance is now mixed with the welded object's at an atomic level.

The 'Possession' perk is both powerful and risky. Have a conversation with the player that chooses it, when they choose it. Let them know how risky the act of possession is in your story's world. For example: In some worlds, the chance that a possessed creature resists is low, and grows with the intelligence of the creature. In other worlds, every being violently resists possession. Be sure to let them choose an alternative perk if they deem the use of the 'Possession' perk too risky.

In some fantasy settings, ghosts have no resistance to magic. That is, magic ALWAYS works on ghosts, even when it might fail otherwise. If this is the case in your story, and a player wishes to take this ability, you should consider informing the player of the risk of being affected by magic while incorporeal.

How Incorporeality interacts with other abilities is subject to GM interpretation - do spells cast by an incorporeal creature only affect other incorporeal beings and not normal, corporeal beings? Generally, I would rule: “No, magic works on both.” But this should depend on the story's needs and be adjudicated consistently.

If a character attempts to move through a very large solid object while incorporeal, a mountain, for instance, it may be possible for them to become disoriented and lost - imagine swimming in dark water. This might be a very dangerous situation for that character.