A/N: Upon no one's request, here's a BAMF!Gaius reveal!

(Much Disclamation)

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"Gaius," Merlin called, traipsing down the stairs from his room with an old stack of parchment, "What do you know about a…" He squinted at the faded writing, "…A Golden? …Hmm… Golden Tunnel?"

Gaius looked up sharply, his eyes shrewd. "Where did you hear that name?"

Merlin frowned, gesturing with the sheaf of papers in his hand. "These old notes, I found them in the back of a book—"

"Forbaerne."

The sheaf ignited and Merlin yelped, dropping it in surprise. It fell to the ground, the paper crumpling and blackening as the flames swiftly eroded every last trace of the neat, spindly writing. Alarmed, Merlin attempted to stamp out the small fire.

Gaius had crossed the room to the rickety old door. He opened it and stuck his grey head out suspiciously, before snapping it shut. "Are there any more?" He demanded, his voice a harsh whisper. "I thought I'd destroyed all of it! Was that all you found that mentioned it?"

Merlin nodded, bewilderedly still stamping at the feeble flames at his feet. "Gaius, what—?"

Gaius hobbled back over, hefted a small bucket from the counter, and tossed its contents at his ward's boots, dousing the fire.

Merlin squeaked, momentarily distracted as his boots were drenched. He looked down at his feet, then groaned. "Gaius, that wasn't the bucket with the leeches, was it?"

"What? No, the leeches are in the tank…" Gaius looked down as well, noticing several slimy, segmented black bodies clinging to his ward's booted feet. His gaze traveled back up and to his left, where the leech tank sat empty and innocuous by the window, "…Which is being cleaned," he realized, his mouth twitching in amusement and sympathy.

"Ngghh," was all Merlin had to say to that. He wrinkled his nose in disgust and shook one of his feet.

"Careful," Gaius warned, already turning away and back to his work at the counter. "There were fifteen in that tank before you emptied it and I expect to find fifteen in it when it's clean."

Merlin grumbled again in vague but grudging assent, and there were several minutes of silence as Merlin attempted to detach leeches from his ankles and Gaius stared rather vacantly at the herbal preparation in front of him, his spectacles perched on his nose, one hand absently rubbing his hip.

It was several more minutes before Merlin was rather sulkily presenting his mentor with a bucket of fifteen whole and healthy (if slightly roughed-up) leeches.

Gaius studied them imperiously down his nose, counting them, before sighing, accepting the bucket, and regarding the grumpy warlock in front of him. "I suppose you're wondering what that was about."

"A little, yes," Merlin confirmed, raising his eyebrows in invitation.

Gaius placed the bucket on the counter behind him and removed his spectacles, rubbing his forehead tiredly. "During the Purge," he began, "There were a few of us who were, for whatever reason, safe— above suspicion, perhaps, or within Uther's protection, like myself. We helped create a network to smuggle people out."

"Magic-users?"

Gaius nodded. "There were designated safe-houses and escape routes and a code system so we could communicate without drawing suspicion, things like, 'I'm out of rue for Len,' meaning a potential raid on the lower town, or 'It's getting windy out, I'll need to re-stock' meaning a west-bound patrol."

"Gaius, that's brilliant!"

Gaius raised his eyebrows.

"Sorry, go on," Merlin grinned unrepentantly.

Gaius rolled his eyes but continued anyway. "I was the ear in the castle, but I had the freedom to move about treating patients and collecting herbs. I was always accompanied by guards— for my safety, I suppose, but also because Uther only trusted me so much— but I could often get word out using the code, if there was to be a raid, or about patrol movements, so the others could move people out or plan the best route."

"And the whole network was called the Golden Tunnel," Merlin said in awe, looking back at his mentor with newfound respect in his eyes. "That is amazing."

"And highly dangerous— no wonder you approve," Gaius said, fondly exasperated. "At one point Uther grew suspicious and I was barricaded in the castle under various excuses," He waved his hand dismissively. "A guard let slip some information about a huge raid on one of our safe houses and I needed to get the information out, but I didn't know how.

"The king was very much into falconry, then, but there was this one wild bird that he just couldn't tame, a merlin." Gaius grinned at Merlin's surprised look, before his eyes grew distant. "…There was something about that bird… And, weak as my magic was, I had always had an affinity for animals. I managed to sneak out of my chambers one night, tie a warning message to the bird's leg, and release it. I had Balinor's charm with me from when I'd patched him up, so I tried to direct the bird to Balinor, who was at a different safehouse near the outskirts of the lower town. I didn't know if it would work; it was mostly hope, prayer, and a lot of magical guesswork, but a few days later I heard around the castle that the raid had been unsuccessful. We'd had nearly twelve people staying at the safehouse at that time, so I knew the message must have been delivered. Balinor had received it in time and had managed to help smuggle all twelve people out. They escaped via Ealdor," Gaius said wryly, "and I believe that's actually how Balinor met Hunith. That bird was, if I am inferring correctly, your namesake."

Merlin's eyes were wide with wonder, veritably glowing with his excitement. "That is brilliant," he repeated.

"And deeply illegal," Gaius said in clipped tones, turning abruptly from his ward to the neglected herbal treatment on the counter. "So I'll thank you to keep mum on the matter."

"But—"

"Mum!"

"But Gaius—"

"Mum, Merlin!"