Reth is an accomplished fighter and he's very skilled at hand to hand combat. His blessing makes him very fast and he can cover his body in scales that protect him from damage. However, it took him a long time to build a strong enough connection to his blessing to do this effectively, so he still has many scars from previous battles. He sometimes uses magic in his fights, which is why he makes sure to have gems on him at all times. 

He left his family when he was very young because they wanted him to be someone he was not and marry him off to a young woman of good standing. It took him a long time to get used to living on his own and he got into many stupid fights over the years. Eventually he settled in Melissandre after being showed there by a mysterious man who he has been searching for ever since.  

Now he lives a more peaceful life, offering his services as a body guard to those who need it.