Thunderfin [better] -

Finn surfaced. His fin was dim now, smoking gently. He looked up at her—a girl of the air, haloed by the setting sun.

To the surface world, he was a myth—a silver streak beneath the hulls of fishing boats, a shimmer of bioluminescence in the midnight deep. To the merfolk, he was a prince of a forgotten line. His fin, unlike the gossamer veils of his kin, was forged of living metal: cobalt scales that hummed with the static of a perpetual storm. When he breached the surface at twilight, his tail crackled with miniature lightning, and the sound was a low, rolling boom that shook the clouds. thunderfin

“I couldn’t let them burn,” he said. His voice was the sound of waves on a shingle beach. Finn surfaced