Bruvac the Grandiloquent doubles the number of cards opponents mill. Small repeatable mill effects become more substantial, while large effects can move a library close to empty in one resolution. The ability is a replacement effect, so it changes the milling itself rather than creating a separate trigger afterward.
Maddening Cacophony is a direct partner. Its kicked version mills half an opponent's library, rounded up; doubling that instruction can mill the entire remaining library. Bruvac needs to remain on the battlefield when the milling occurs for the replacement to apply. Removing him before the spell resolves changes the result substantially.
Altar of the Brood offers a slower route by producing repeated small mill events as permanents enter. Bruvac improves each qualifying event, but only effects that actually instruct an opponent to mill receive the increase. Discarding, surveilling, or putting a revealed card into a graveyard through a differently worded instruction is not automatically milling. A mill deck also needs to handle the resources it gives opposing graveyards before their libraries run out. Graveyard interaction and a planned finishing sequence can matter more than maximizing every individual mill number. Bruvac fits a focused blue mill strategy where several cards benefit from his static ability. Protect him for the turn when the decisive spell resolves, and evaluate the remaining library rather than assuming every large mill effect ends the game immediately.
