UndeadInvasion is a custom game mode for King Arthur's Gold, based on Eanmig's zombie mod, which in turn is based on an official mode in a very early version of the game.
In UndeadInvasion, the players are called to aid the kingdom in a massive invasion of the undead. Previous inhabitants of the kingdom are crawling out of mausoleums and graves for reasons unknown. It is up to the king's loyal servants to secure each area by hindering the undead from destroying special points-of-interest, and to permanently destroy the local sources of undead.
To install, simply copy the files into a folder of preferred name. To play UndeadInvasion, open "mods.cfg" in the installation directory for King Arthur's Gold, and append a line with the folder name you chose. Next, open "autoconfig.cfg" and change the line and change the value of "sv_gamemode" to "UndeadInvasion".