The Lost Brigades Expansion is special because it allows players to incorporate these new units into their faction's core units, without requiring a Commander Card call-in. Alternatively the 60 building board extender tiles offer a play-mode that allows players to add units from across their entire collection into their faction's building boards.
Lost Brigades vehicles also emphasize the new Assault rules found in the second edition. This can dramatically flush out a faction's options and strategic decisions from early on in the game. Each Lost Brigades vehicle also comes with two commanders that allow players to further specialize and upgrade that vehicle, or alternatively they can field the core Lost Brigades vehicle and choose an entirely different commander to gain access to an even wider range of units.
—description from publisher