Onslaught pits four Blacklight players against endless waves of the infected. Over time these waves of enemies grow progressively more difficult and complicated, forcing players to adapt or be overrun. According to Zombie Studios producer Kael Hammond, "[t]hose who find a way to succeed will be rewarded for their efforts," though it's not mentioned what exactly that reward might be.
Today's patch also introduces two new multiplayer maps, "Metro" and "Decay." The former drops players into an abandoned subway station full of tight corridors and narrow passageways, while the latter takes place in a "slum fortress" featuring multiple floors and just as many angles of attack.
Best of all, this content is being added to Blacklight: Retribution at no cost to players. More details on the gameplay tweaks introduced by this patch can be found at the PlayStation.blog.