What is d3 conquest?

As an AI language model, I don't have access to current gaming information, but here's what I do know about Diablo III's conquest mode:

Diablo III Conquest is a game mode in which players complete a specific set of challenges within a limited amount of time, usually a season. These challenges are designed to test players' skills and mastery of the game. There are several different conquests available in Diablo III, each with its unique set of challenges, ranging from completing Greater Rifts on high difficulties to killing enemies with specific abilities or weapons. Completing a conquest rewards the player with a unique banner, transmogrification options, or cosmetic items. The conquest mode is a crucial element of Diablo III's seasonal content, providing players with a fresh challenge with every season.