He loosened it (Patreon)

Thankfully, Brann never made a promise to sleep with the one who bests him.

Well, he did, some fifteen years ago. But he only held that vow for two and a half days, when he met Glenda, waitress and part-time seamstress. She was very happy Brann had defeated all those bandits who were raiding the town and wanted to show her appreciation.