I couldn't finish 'em. Looks like this's gonna get complicated.
Abyss Worm is an enemy in Final Fantasy IV: The After Years. Despite its high HP and Strength, it is not a dangerous enemy, and will mainly use Bloodfeast to restore its HP each time it is attacked. A Fire spell kills it easily.
Abyss refers to a bottomless pit, to the underworld, to the deepest ocean floor, or to hell, or more loosely to any chasm or large drop.