Aftermath is a hl2 mod which involves the player killing waves of the undead with your friends or alone using weapons, your knife or even blow them up with grenades and set them alight with Molotov's.
This mod is poorest I ever seen; One reason why I rated it as 1 out of 10 because it had no mission, and I noticed upon running this mod, most detested multiplayer menu... It is more confusing menu and fonts is not clear... I am not joking about it... Hmm, I think it deserves lowest rating ever!!!