Jal-Nib is one of the monsters which can be found in the Inferno.
Several of these creatures spawn per wave and can cause damage to three pillars found within the arena. Once a pillar is damaged enough, it will fall.
All of the Jal-Nib spawn near each other about midway between the three pillars. They will then move towards one of the pillars to attack it, ignoring the player. If all pillars are destroyed, they will attack the player instead.
Jal-Nib are often referred to as nibblers because they attempt to eat the pillars that stand in the Inferno. The TzHaar word Jal was revealed in RuneScape 3 to mean foreign, or not TzHaar.