Like a painless fist full of needles, the numbness slams into the rest of his cognition, the transition curt, palpable out of some strange hesitance. It's as if a chain reaction grasped his mind and converted his thoughts into hard crystals, as if his skull were full of water being flash-frozen. His consciousness shrinks to a pinprick, swallowed up by a black hole.
And then it's gone. It's gone, but he's still thinking. The pain is still registering. There's still a disembodied awareness of his surroundings, of the pinprick eyes, of the impossible darkness wrapped around him. A greater awareness, by some measure, an almost infinitely more numb one in another. Not quite fully there. Not quite fully self. But enough to know that self was missing.
For Cheshires, water is a problem. One Cheshire's experiments (Theta) with water, searching for some way to reliably endure the substance, some way to survive the weakness or sickness it brings, occasionally take on a literal life of their own.
Thorns (sometimes called Chesters) are hybrid creatures, part animal, part Cheshire. The hybridisation is not genetic - a Thorn still has their full set of animal DNA, and a full set of the equivalent Cheshire structures. On a technological level, they are best considered Cheshires with avatars - Cheshires protective of the flesh they've taken on, identifying with it. The reason for this identification can be varied:
Generally speaking, Theta takes care to conduct his experiments with non-sentient donations of Cheshire 'cells' taken from himself. That said, a collection of Cheshire cells, while there is a chance they might remain dormant, are notoriously difficult to keep from dying or from expanding into something pre-sentient, then sentient, then loosely sapient. The fine line takes careful balancing. Theta would rather err on the side of a sentient experiment, as a dead one would not serve his purposes well.
The following things need to happen for an original Thorn to arise:
This means that only about one in fifty of Theta's experiments becomes an original Thorn. Three months into the subjugation of humanity, he's done approximately 120 experiments. Of those, an early one resulted in Adrian Roche, the founder of Nightshade1).
Thorns are not necessarily human, though sapient Thorns almost exclusively are.
It's possible for Thorns to create other Thorns (by deliberately doing what Theta did on accident), but it requires a Thorn with an actual understanding of the process of fleshgrafting. In addition, given that it's a personality-destroying process, it will likely rarely be done.
As Thorns are simply Cheshires grafted to flesh, they inherit all of the Cheshire abilities and weaknesses, though their fleshbound nature alters quite a few of these:
Technically, Thorns could rearrange their fleshselves into any other form, but this would take a lot of time and care, possibly killing the flesh component.
Thorns continue being weak to water. They can drink it and digest it (their Cheshireself is grafted to those parts of the flesh that aren't preoccupied with these things) and if their Cheshireself is small enough they can swim through it, but their Cheshireself is just as vulnerable to it as a proper Cheshire. The high water content animals typically possess tends to cause Thorns a very low background level of chronic pain, but it's low enough that they may not be conscious of the effect.
Despite the ability to swim through water, Thorns are typically extremely thalassaphobic. They also tend toward being rather dehydrated, due to their avoidance of water.
All that said, one of the disadvantages Thorns have toward Cheshires that have nothing to do with any physical handicap is that, being rather human in their thought processes, including empathy, they are not really laid out toward differentiating Cheshires from other Cheshires other than by the territory that they claim.
This extends to their own kind, meaning that they would not, from appearances alone, be able to determine that a supposed Thorn ally they’ve had a year of experience with is actually a Cheshire spy since the past week.