3e SRD:Ability Score Loss
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Ability Score Loss
Various attacks cause ability score loss, either temporary ability damage or permanent ability drain. Points lost to temporary damage return at the rate of 1 point per day (or double that if the character gets total rest) per each damaged ability (in other words, if you have lost both Strength and Dexterity, you naturally regain 1 point per day of both ability scores), and the spells lesser restoration and restoration offset temporary damage as well. Drains, however, are permanent, though restoration can restore even those lost ability score points.
Some spells or abilities impose an effective ability score reduction, which is different from ability score loss. Any such reduction disappears at the end of the spell’s or ability’s duration, and the ability score immediately returns to its former value.
A full hit point score, however, can’t drop to less than 1 hit point per Hit Die.
The ability that some creatures have to drain ability scores is a supernatural one, requiring some sort of attack. Such creatures do not drain abilities from enemies when the enemies strike them, even with unarmed attacks or natural weapons.