343 Industries announced the introduction of a new free DLC pack for Halo 5: Guardians, called Battle of Shadow and Light. It is a mini-expansion for the multiplayer side of the game, and it introduces 48 new REQs, a new Shinobi armour based on ninjas, a a new legendary rifle, and the much anticipated Big Team Battle mode.
There are four specific maps for Big Team Battle, which pits two teams of eight players against each other, and the maps are available across Custom Games and Matchmaking. You can find more concrete details about Battle of Shadow and Light on the 343 Industries official website.