The texts are confused, and I’m also confused.
7 is a majority opinion when all the texts contained in the game are seen. 9 may be a typo. Probably, one of eight is a fake.
In tags_skills.txt, 8 item skills say plague of Dreeg as “7”.
[li]tagItemSkillD149Name=Plague of Consumption[/li]tagItemSkillD149Desc=Unleash one of the seven plagues of Dreeg, a powerful contagion that saps vitality and spreads rapidly.
[li]tagItemSkillD150Name=Plague of Corruption[/li]tagItemSkillD150Desc=Unleash one of the seven plagues of Dreeg, a powerful contagion that causes bewilderment and spreads rapidly.
[li]tagItemSkillD151Name=Plague of Dreeg[/li]tagItemSkillD151Desc=Unleash the crowning achievement of the witch god, a virulent disease that will leave your foes in shambles.
[li]tagItemSkillD152Name=Plague of Fatigue[/li]tagItemSkillD152Desc=Unleash one of the seven plagues of Dreeg, a powerful contagion that causes fatigue and spreads rapidly.
[li]tagItemSkillD153Name=Plague of Rot[/li]tagItemSkillD153Desc=Unleash one of the seven plagues of Dreeg, a powerful contagion that infects with toxins and spreads rapidly.
[li]tagItemSkillD154Name=Plague of Rust[/li]tagItemSkillD154Desc=Unleash one of the seven plagues of Dreeg, a powerful contagion that eats away at armor and spreads rapidly.
[li]tagItemSkillD155Name=Plague of Shattered Souls[/li]tagItemSkillD155Desc=Unleash one of the seven plagues of Dreeg, a powerful contagion that saps the spirit and spreads rapidly.
[li]tagItemSkillD156Name=Plague of Terror[/li]tagItemSkillD156Desc=Unleash one of the seven plagues of Dreeg, a powerful contagion that incites fear and spreads rapidly.
Edit: maybe
Plague of Dreeg = Plague of (Consumption, Corruption, Fatigue, Rot, Rust, Shattered Souls, Terror) = 7 ?