this mod adds a new mobs to the game, called undead mobs, and few of them are in updates, so few of them are in currently version that to be added 
Undead Mobs is a mod that will add a zombies to the game
Undead Pig - this pig that was added on this mod, a mob that burns in daylight and they just similar to the zombies, it's an undead version of the pig and it's like zombie-like pig.
Undead Cow - this cow that was added on this mod, they have similar to the zombies, and they just burn in daylight, this one is undead version of the cow.
Undead Creeper - a creeper that was added on this mod, when they die, they explode, and they have similar way when they die from using by explosion of them, it's an undead version of creeper.
Headless Creeper - a way similar to the undead creeper, but it spreads a blood on the body when he hasn't a head, way similar when they die, they just do explosion when they die
few of them are currently from ideas from way but they will be added in the updates