You'll see that this is a tidbit in more ways than one.
Long Month of Doom, Month of Waiting
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Verser arrives in a world where a vampire and his children raged out of control. Each one infected one more each night.
Day One: The First Vampire.
Day Two: Two Vampires.
Day Three: Four Vampires.
Day Four: Eight Vampires.
Day Five: 16 Vamps.
Day Six: 32 Vamps.
Day Seven: 64 Vamps.
Day Eight: 128 Vamps.
Day Nine: 256 Vamps.
Day Ten: 512 Vamps.
Day Eleven: 1024 Vamps.
Day Twelve: 2048 Vamps.
Day Thirteen: 4096 Vamps.
Day Fourteen: 8192 Vamps.
Day Fifteen: 16,384 Vamps.
Day Sixteen: 32,768 Vamps.
Day Seventeen: 65,536 Vamps.
Day Eighteen: 131,072 Vamps.
Day Nineteen: 262,144 Vamps.
Day Twenty: 524,288 Vamps.
Day Twenty-One: 1,048,576 Vamps.
Day Twenty-two: 2,097,152 Vamps.
Day Twenty-three: 4,194,304 Vamps.
Day Twenty-four: 8,388,608 Vamps.
Day Twenty-Five: 16,777,216 Vamps.
Day Twenty-Six: 33,554,432 Vamps.
Day Twenty-Seven: 67,108,864 Vamps.
Day Twenty-Eight: 134,217,728 Vamps.
Day Twenty-Nine: 268,435,456 Vamps.
Day Thirty: 536,870,912 Vamps.
Day Thirty-One: 1,073,741,824 Vamps.
Day Thirty-Two: 2,147,483,648 Vamps.
Day Thirty-Three: 4,294,967,296 Vamps.
Day Thirty-Four: Six Billion, and not everyone got to party that night.
Day Thirty-Five: Hunger Pangs.
Day Thirty-Six: Hatred as Vamps find there is no more prey, and they can't prey on each other.
Day Thirty-Seven: Excruciating Pangs, and Murder.
Day Thirty-Eight: Vampires due to lack of blood go to sleep.
Day Fourty-five: Green grasses are growing across intersections.
Day Sixty: Verser arrives full of nice tasty blood which six billion or so vampires can smell....
The verser sees an empty world with some corpses as he arrives in daylight. Weeds sprout in the streets. A newspaper tells of a riot. Another newspaper tells of the Air Force running out of napalm to control the 'Spread'. Piles of garbage that has been burnt, and some flung about still burning fill an area near an alley. Some graffitti on a wall shrieks out "The HUnger!".
Night falls.
If the verser is very resourceful, he survives to midnight.
Variants:
1. What about the animals? Are they drinkable? If they are, then the vamps survive a bit longer as they exterminate the animals of Earth.
2. Can the animals be turned?
3. This version assumes that vampires cannot feed on vampires. However, if they can, then the population will be markedly less as predator hunts predator. And there will be signs of small-scale, but very brutal warfare throughout the city.
4. How did the original vampire come to be? Was this creature a verser who arrived, and then destroyed a whole planet for amusement's sake, and to make a statement about how Good does not exist?
5. Will the verser get a chance to meet the First Vampire? Perhaps after the verser is trapped somewhere? That way, both sides can have a nice chat before the slaughter.
6. The magic bias is dependent on what type of vampires these creatures are.
And Tidits...well, this is a short world setting, and the verser is just a tiny morsel, a tidbit to the feeders in the night.