So I hate reading poorly written fight scenes in fantasy books. Whenever my characters fight, I try to make it as realistic as possible. Here's how you write a concussion:
Holt caught a glimpse of a flanged mace heading right for the side of head, breaking his momentary confusion and forcing him to fall to the ground to avoid being killed in a single blow. The edge of the mace caught his helmet with a loud crash, instantly disorienting him and replacing all the sounds of battle with a harsh, screeching ring in his ears.
Luckily, his attacker overbalanced in the assault, and Holt wasn’t simply obliterated by a second blow from the fearsome weapon. Clutching his stolen axe like a cane, Holt pulled himself to his feet and tried to steady the spinning world. He felt drunk, overwhelmingly drunk, and a wave of nausea crept into the back of his throat as he failed to get his bearings perfectly straight.
The mace-wielder turned back, a wide grin splayed across his unarmored face. He slapped the head of his weapon in his open palm, and Holt saw a few streaks of blood rub off on the man’s skin.
The captain tore his helm from his head and tossed it aside. The fresh air seemed to calm his roiling stomach, but only by a fraction. When he looked ahead, he could barely focus. Everything was blurry around the edges. The man came forward again, swinging his heavy mace from left to right. Holt raised his axe to block, and the mace head shattered his weapon’s shaft into a hundred splinters.
“Now you die!” the attacker bellowed. The man’s teeth were yellow and jagged, and his breath smelled like vomit.
Holt stifled a chuckle when he realized it was his breath that carried the pungent stench of stomach acid, not his attacker’s. Still spinning helplessly in his own mind, he tumbled back to the ground unarmed, heaving the contents of his gut across the stones at his feet.
The captain fell onto his side with a sullen whimper, waiting for the killing blow to quickly bring an end to his scrambled senses. After a few seconds, he realized it likely wasn’t going to happen.
He wanted to open his eyes, to see what fate had befallen his attacker, but he knew it would be useless. Even with his eyes shut, all he saw was a shifting field of slowly spinning color blotches that made him scream in agony. The screaming brought on another round of painful vomiting, and then everything finally, mercifully, went black.