This page lists all of the enchantments added in AbyssalCraft, with information on their usage.
The Coralium enchantment functions like the Fire Aspect enchantment. Upon hit, it applies the Coralium Plague (instead of setting the entity on fire).
The Dread enchantment works like the Coralium enchantment, except it applies the Dread Plague.
The Iron Wall enchantment is a "anti-knockback" enchantment; ie. it negates any knockback from enemy attacks.
Potion Effects (more explained):
Coralium Plague deals 1 heart of damage per second (at a rate between Poison and Wither).
Dread Plague deals 1/2 heart of damage per second, while also reduces your food bar (like the Hunger potion effect does, de-saturating it).