You are a priest fighting werewolves, vampires, and other nasty shit using your arsenal. The game begins at dusk, with some very casual shit going around. As the game gets further and further along, the amount of enemies and the degree of difficulty involved gets higher and higher.
Your beginning weapon is the Pistol, which is a pistol. It scores normal damage, but has unlimited ammo. You can pick up special cross-clips which can be equipped to any weapon, including the pistol, to make the bullets silver.
Later on you can pick up other standard things, like the Shotgun, Rifle, Rocket Launcher, Flamethrower, and Machine Gun, which all behave about as expected. You also get the Holy Water Gun, which shoots holy water; the Pile Bunker (pretty much the heaviest damage); and the Holy Sword (pseudo-melee; does massive damage up close, but also lets out slashes of light at short range; unlimited ammo). You can pick up grenades in the form of bottles of Holy Water or flaming oil.
Enemies:
Basic shit. They move very slowly. Take a few hits to kill, but the head is a weak spot.
Not as tough as Zombies, but very resistant to bullets. They fight using a sword and shield, meaning they can block the Holy Sword.
Like Skeletons, but with armor and better skill, making them super-tough. They can use their shields to block all damage.
Pop up from the ground behind you - a sound and weird white flashes on the screen is all that tells you they're here. No damage, but one touch causes paralysis. Slightly tougher than zombies. Silver does extra.
Big flesh golem. Like zombies, but much stronger and faster. Immune to holy and fire. One punch kills you. Use the rockets.
Tougher Skeleton Knights with magic fire-balls. They have a magic barrier which blocks all harm - Holy Water or a Holy Sword will dispel it, allowing them to be harmed. Silver does extra.
Immune to everything but silver. Very tough. Super fast. Hit very hard. Regenerate after death.
Immune to everything but silver, holy, and fire. Have a few magic spells. Drain huge amounts of life with a hit, healing themselves in the process. Slightly slower than Werewolves. Regenerate, but you can use a stake to keep them from coming back.
There are a few bosses as well, like the Giant Flesh Golem (appears at 8pm), the Barrow Lord (appears at 10pm), the Werewolf Leader (appears at midnight), and at the very end Dracula (appears at 4pm; only sunlight kills him, meaning you have to wait it out). Every hour reflects 10 minutes of play. There are different maps, with different enemies; the Snow Map spawns shape-shifting Draugr, as an example. Demons will also sometimes spawn, which are basically mini-bosses, and can only be killed with the Holy Sword.
Beating a full night means you get to get your High Score posted in the records. You can keep looping, with each night getting progressively harder. Bosses keep getting replaced, until on night six, you're dealing with the Dunwich Horror (it's invisible lol) and eventually Satan as the secret final boss (good luck faggot).
Oh, and speeds should be Unreal-tier.