Halo 5 February Update will add Assault, Grifball, and Fiesta gametypes as well as a bunch of custom game settings and forge tools so that fans can create (or recreate) any ball game type they want!
These game types and tools will be added with the February content update, Hammer Storm, which is set to come out later this month.
Source: HALO COMMUNITY UPDATE – A WHOLE NEW BALL GAME
Is fiesta only in custom, or forge games?!?!? I’m pissed off if so, I want to play it in Arena but I can’t find it!!😡😩