In this system Defenses show how safe the character is from the hurt of the world. For now, it is best correlated to Armour Class.
The higher defenses are, the less the character is vulnerable to the world, the more they are detached and disconnected from anything that world is able to throw into them. The flip side of the coin, is that the more the character is disconnected from the world, the less they are capable to perceive and interact with it. Beyond the highest defense (cocoon) there is no need whatsoever to roll saving throws as the character is a static object with no vulnerable mind or body.
Here the type of the defense is not strictly speaking the same as physical armour, it rather shows the layer of general impedance between the character and the world. 'Disc' can be a full-body shield or an armour made of ceramic discs, plate can be of metal or chitin, 'shell' can be of concrete. 'Flesh' and 'skin' mean character's own flesh and skin, i.e. skeletons are all have precognition, telepathy and aura insight.
The chart is cumulative: plate defense makes the wearer to give up precognition, telepathy, aura insight, touch, smell, hearing and dreams.
I don't know yet how to explain that some entities are capable to partially keep some of the senses and how some other entities lose more than usual. The working idea that certain paths adjust this chart up or down by one or more steps.
As an optional rule the Defenses can be raised in any moment but never or almost never can go back down.