Have a link/source for that? Looks suspect
This passage in is Mark 5 and Luke 8. It tells of a man possessed with multiple demons who exhibits super human strength who encounters Jesus.The demons, speaking through the man, give their name as LEGION.
In those days, LEGION referred to a Roman army organization. A Roman legion (from Latin legio "military levy, conscription", from legere "to choose") was the largest unit of the Roman army, involving from 3000 men in early times to over 5200 men in imperial times, consisting of centuries as the basic units.
The passage describes the legion of demons being cast into a heard of 3000 pigs, which drown themselves instead of going to the abyss.