The phrase is Portuguese gamer slang, with “valeu” used as a casual way to say thanks and “duo” referring to playing a game with a partner. Riot is the name used by players for Riot Games, the company behind League of Legends, so the line reads as a thank-you aimed at the game after a duo session. Short clips like this spread through soundboards and gaming chats because they are easy to recognise, quick to drop into a video, and carry a friendly tone that fits wins, highlights, and light-hearted reactions.