The ghost sprite used in the game.
Background story
Pokémon black is a creepy pasta based on the popular pokémon franchise. The meme claims that a hack from the pokémon game pokémon red exists in which the player has the ability to kill trainers and pokémon. This can be done by using a ghost that knows the move curse on pokémon and after battle (do note that the creepy pasta explicitly tells the reader that the move didn’t exist back then).
This meme however does not relate to the ds pokémon game: pokémon black version because this is about a hack of a gameboy game.
After acquiring your first starter pokémon, the player the pokémon “ghost” will be added to the party.This is where the game begins to take a very dark turn.
Excerpt “Defending Pokémon were unable to attack Ghost -- it would only say they were too scared to move. When the move “Curse” was used in battle, the screen would cut to black. The cry of the defending Pokémon would be heard, but it was distorted, played at a much lower pitch than normal. The battle screen would then reappear, and the defending Pokémon would be gone. If used in a battle against a trainer, when the Pokéballs representing their Pokemon would appear in the corner, they would have one fewer Pokéball. The implication was that the Pokémon died.
The Full Story can be found here
Real game?
The likelihood of this game existing however is very small, one would need to hack the game to great lengths to be able to kill a player and to be able to show on who the player used curse on afterwards.
In an effort to recreate the alleged hack, fans are in the progress of making their own hack based off the gamboy advance game pokémon fire red. Their youtube account can be found here, they also keep up their own blog to update fans of the project about their progress: project creepy black.