From Bulbapedia, the community-driven Pokémon encyclopedia.
Rend is a mysterious man with a somewhat goofy personality. He seems to well respected in his village, as shown when the villagers are seen breaking up a fight at his request. He has a tendency to start laughing, even when he is fighting someone he believes to be an enemy.
Despite his quirks, Rend is very knowledgeable about the mechanics of Burst and even knows how to send a person inside of a Burst Heart.