From Dungeons of Dredmor Wiki
A lingering weakness afflicts you due to contact with dark magics.
Debuff: -1 for 93 turns
Lingering Weakness is a detrimental effect (Curse) that affects characters that cast spells such as Deathly Hex and Mark of Chthon.
It is a side-effect of spells cast by characters with the Necronomiconomics skill tree. It can also affect characters that drink from a Fountain or consume Dwarven Gut Rot.