Found this cool post about the “false hydra”, a monster from Dungeons and Dragons.
Born of lies, the False hydra sprouts as a lump of flesh below a city. An adolescent false hydra can have 3 heads, on long flaccid necks up to 120 feet long. A fully grown elder Hydra can have 8 or more heads, each on necks up to a quarter of a mile long.
The long pale faces of the hydra burrow underneath the city, surfacing in basements and lower levels of buildings throughout.
It devours animals, people, really anything with a pulse. And it grows every time, gaining heads as it goes.
When fighting a hydra, it’s range and amount of attacks are decided by the amount of heads it has. The more heads, the deadlier it is. It can also let loose sonic bursts, damaging all in its path and stunning unsuspecting creatures.
If that was not scary enough, you must then consider the real ability of the False Hydra, the Hydra’s Song. This ability has no saves, there is no way to avoid it besides deafening yourself. It also has a 5 mile radius, radiating out from the singing head.
This song has memory altering abilities, the hydra can selectively erase the memories of all within its range. If it reaches through the ground and eats the miller out of his bed at night, the miller’s wife will be left wondering why her closet has a man’s clothes in it. The towns people will wonder why the old miller gave the mill to an unmarried woman unrelated by blood. The farmers may remember where they got their grains milled, but will be confused as to who did it for them.
Try asking a towns person where you can find the mayor and they may answer there is no mayor, they havent had one in years. But you are confused, you just visited the mayor’s house, and it looked like it was lived in quite recently. What you didnt see, or at least you dont remember seeing, was the pale bloodstained face staring at you from a hole in the wall.
And after the entire town is devoured, the hydra moves on. He goes to the next town, digging and devouring until there is no-one left. And nobody ever thinks to stop him in his travels, because as soon as they turn to tell the guard about the gargantuan monster walking through their fields, they forget it ever existed.
This is the power of the False Hydra, easily one of the most powerful enemies, and certainly one of the scariest as long as your DM is up to the challenge.