The Grade 1 Calamity Curse could be used up to nine times a day, and it'd only be able to affect Third Layer Hundred Year realm level Demonic Beasts a little. There was a chance to kill Second Layer Hundred Year realm level Demonic Beasts, and it would at least heavily wound them.
The Grade 2 Calamity Curse could be used six times a day, and would cause a bit of an effect on Fourth Layer Demonic Beasts. There was a chance to kill Third Layer Demonic Beasts or at least wound them heavily.
Grade 3 Calmity Curse had a tiny effect on Thousand Year King level Demonic Beasts, and had a decent chance to cause the death of Fourth Layer Hundred Year realm level Demonic Beasts, or a guaranteed chance of heavily injuring the latter at the least!