Ethereal plane/ Etherealness

One cannot speak of an ethereal plane or state of etherealness without first considering the principles of the Weave. All matter is tied to the weave and some material tends to tie itself to more weave. Creatues are inherently tied to the weave both through physical body and through their souls, meaning that they have both a physical and non-physical connection. Since one does not need to possess physicality to join themselves to the weave, there is a state of etherealness in which one change the weave of the physical body by loosening the threads of the weave until it only remains as a sliver and the body turns to nothing. While ethereal movement is no longer bound by physical constraints and travel becomes like flying through air, Becomming ethereal, although tricky, is nothing compared to returning to physical form.
The connection to the weave is naturally weak while ethereal as one would have to sever their physical channels and creating detailed matter is far from simple. Although the blueprint of the physical body still remains within the weave, it does not move naturally to recreate something that has gone ethereal but prefers to move along already existing material matter. The easiest way of perfoming etherealness is by designating the return of the spell before turning ethereal, this is the principle why a spell such as blink works.

"Turning ethereal is just a matter of sepperating your physical form from the physical plane and the returning it. Imagine that you are plucking the hairs of your arms one by one before AAAAAAAAAHHHHHHHH" The skin of the professor dissapeared as though it had never been there and his magical cloak fell upon his bare flesh, turning his lecture into a sight of the torture chambers from the nine hells. The shouting did not last long as blood poured out of his body and he crumbled to the ground, a red pile of flesh covered by the brand new magical cloak that had accelerated the ethereal transformation surrounding it.

Protections

Fortifications run the natural risk of being scouted through etherealness at any point or simply having enemies return to physical form within the walls, defeating the entire advantage of a fortification. Although few would use etherealness a reoccuring plan due to its inherent dangers, fortifications can greatly increase the threat of staying ethereal by simply filling the castle with items that naturally attract the weave, such as hugh amounts of gold and gemstones, or by setting upp magical tools that continually manipulate the weave and move it.


A dragon hoard or vault of gold are both natural targets of theft but are at the same time natural detergences against ethereal attacks as the weave does not want to spend time weaving something else in the hoards presence. In addition, turning the hoard ethereal presents a great challange as the weave does not wish to sepperate itself from it.