"They say there's ancient treasure in the cave."
"Who are 'they'? They're probably just making it up."
"Come on, Merlin, let's have a peek. What could go wrong?"
"Everything, as usual?"
"Don't be such a wet blanket." Arthur rolled his eyes at Merlin and stepped inside, walking cautiously, sword in hand. Merlin had no choice but to follow him.
The dim light from the entrance had mostly faded when Merlin noticed the crystal. It was large and jagged, embedded in the rock, and it suddenly came alive.
"What is that— " Arthur asked, but his words somehow slid past Merlin, going unheard.
In one flash, turning bright as the sun, the crystal grabbed and held Merlin's mind, as a magnet draws iron. He was pulled towards the strange luminescence, unable to resist. Staring into the crystal's bright depths, he saw colours, light, the present, the past, and the future, all of it jumbled together. It was overwhelming. Irresistible. Invincible.
"That thing must be magic, Merlin," Arthur told him. "It might be dangerous. You were right. Avert your eyes. Let's leave."
It was too late. Merlin was trapped in the depths of the crystal, experiencing a complete sensory overload that left him no free will. He couldn't blink, couldn't move. Arthur's voice didn't register. The images kept coming, an endless barrage, with sounds and smells and sensations that only Merlin could experience. The crystal's magic had latched on to his own and held it captive.
"Merlin!" Arthur tugged at him. When Merlin didn't react, Arthur shook him. "You were right. This place is dangerous. We must get out. Now!"
There was no response. Merlin was lost to the crystal's flow of dark magic.
"Right," said Arthur, setting his jaw and sheathing his sword. "We're leaving."
He grabbed Merlin in one forceful motion and hoisted him onto his back, stumbling as quickly as he could towards the cave entrance, one step at the time. "You've always been a dead weight, Merlin, but when did you become this heavy?" he muttered, his knees nearly giving out.
Merlin didn't answer, except for a continuous high-pitched and pained whine of protest. The sound hurt Arthur's ears. He kept going.
Away from the cave, Arthur gently placed Merlin on a patch of long green grasses in the sun. He sat down beside him, panting and wiping sweat from his forehead. "Come back, Merlin. You can do it."
It took some time, but finally Merlin blinked and sat up, confused and dizzy. "Where are we?"
"You don't remember?"
"Oh! The cave. The crystal."
"Indeed. You seemed to find it very— captivating."
"You saved me?"
"I do need someone to polish my armour, you know."
Merlin closed his eyes. He was beyond exhausted. Dark magic still flickered and roiled at the edges of his mind. That had been a close call. Too close.
Arthur let him have time, but eventually he got to his feet. "We need to move on before it gets dark. Can you manage?"
"I think so." Merlin got up slowly, feeling like a creaky old man. "Thank you, Arthur. I've saved your life so many times, it's nice to have you repay the favour."
Arthur laughed. "You're better, I see. Your preposterous humour is back."
Merlin grumbled. "It wasn't a joke."
"Of course not," Arthur said, still grinning. "Let's go."