Arthur has a thousand scars, and Merlin knows them all. They litter his hands and fingers where he's been nicked by practice blades too many times to count, and meander along his forearms where armour gaps.
There are two impressive gashes alongside Arthur's ribs from assassination attempts and a satellite one on his left shoulder from where he was pierced by a jousting baton. There's even a little one high on the inside of Arthur's left thigh where a night of drunken revelry and a poorly stacked fire lent itself to unsuspected danger.
Like all men, Arthur's shins sport the evidence of having crashed through the underbrush, but as a leader, his are probably worse. And there is even a scar on the bottom of Arthur's foot from a broken sewing needle that Arthur had gouged out on his own rather than admit he'd been sneaking around with the seamstress' son.
Merlin knows them all by heart and by feel. He caresses them with the drag of the flannel each time he bathes Arthur, touches them with his fingers while he aids his king in dressing. And when they lay together, Merlin worships them with his lips and tongue, working Arthur into a frenzy because each scar is deadened to sensation, and Arthur can see but hardly feel Merlin's devotion until Merlin decides to prove it in other ways.
Merlin loves each of Arthur's blemishes. Each one is a testimony of Arthur's survival, and that he is more God than man.