-Your pokemon has to be a higher level than the target.
-The target can't have a type immunity (ex. horn drill on Gengar won't work)
-You've got to be lucky. Not a condition, but 30% still isn't that great.
Does damage equal to the target's max HP. If the target uses Endure or is holding a Focus Sash, it will leave them with 1 HP.
Accuracy = ((U—T) + 30) / 100
U=Level of user,
T=Level of the target