No sooner was Thor asleep than he was in motion. Loki drew a deep breath, and re-grasped his mental hold on Thor’s nightmare like a rider pulling tight on the reins of a rowdy horse. Flickers of images slipped past his mind. Shadows, mostly, shadows given the ability to grip, grasp, slice and stab; a face more snake than man, thick hands, and a soft, calm voice. In reality, Thor thrashed against the dank stone floor Loki had given him the sleeping draft on (after all, you don’t want to have nightmares in your own bed), and twisted his own body as if he were helpless and restrained, his thick arms, bound by nothing, pressed tight and shivering against his writhing back.
“Not again,” he groaned, as blood-flecked spittle formed on his lips and began to leak from between his clenched teeth. “No more.”
“It’s a dream, Thor. A nightmare. Gorr is dead. Loki is here. Your brother is here. We’re going to erase this pain from you.”
Thor’s labored breath slowed down a bit, and Loki pulled himself closer, weighed down by the density of Thor’s struggle, and put steady hands on either side of Thor’s head, to keep him at least from grinding his skull into the floor, or breaking his own neck. Rage was distracting him. He should be concentrating on the distress - on drawing it out through Thor’s throat and giving him peace - but every time he tried to look directly at it…
Rage. Blinding, stomach-boiling rage. How dare he. How dare he. He was hearing mostly Thor’s voice, now, both dream and real, weak where it should be strong, whimpering instead of snarling, surrendering over and over again, succumbing to a stranger.
“Enough,” Loki heard him choke out, and took a sharp breath in as he, again, failed to grasp the nightmare, his palms slippery with sweat and only holding tight to the damp golden strands of Thor’s hair. “Gorr…enough…I yield…”
“Gorr is dead, Thor,” Loki hissed, shaking his sleeping, suffering brother with a tightening of his claws. “Gorr is dead. Lie still, you are safe.”
[So the explanation for this is that God of Thunder is really really good but also I’m a bad person who apparently wants Loki to attempt to give Thor exposure therapy to his nightmares but ends up mentally scarring himself with blinding rage more than doing anything productive.]