The appearance of a Mountain Hag is so hideous as to require any character of less than 5th level to save vs magic or lose 1-10 strength points for 1-8 turns; Clerics and Paladins are allowed a bonus to this saving throw equal to their level.
The Mountain Hag fights using a filthy, jagged and rusty dagger (D 1-4), which has a 75% chance of carrying a disease (treat as chronic, severe, affecting blood and gastro-intestinal organs - see Dungeon Masters Guide p14).
A Mountain Hag can fly, 1/day, paralyse (as a wand of paralysation) by touch, 3 times/day, and cause darkness, 3 times/day. She can use magic-user scrolls as a 10th level thief, and can also speak with animals at will. There is a 30% chance that a Mountain Hag will have a familiar, of a type determined as for the first level magic-user spell find familiar.
A Mountain Hag may call down a terrible curse on one victim, who must save vs magic or lose 1-4 constitution points, and must make all subsequent saving throws vs poison or disease at -2 while the curse is in effect. Any wound sustained during this period will heal at half the normal rate, and has a 25% chance of becoming infected. The curse lasts for one lunar month or until the victim dies or receives a remove curse spell. A Mountain Hag may only have one curse in effect at any given time.
Finally, Mountain Hags are immune to poison and disease, and make all saving throws against mind-influencing spells at +2.
SRD said:Horrific Appearance (Su): The sight of a sea hag is so revolting that anyone (other than another hag) who sets eyes upon one must succeed on a DC 13 Fortitude save or instantly be weakened, taking 2d6 points of Strength damage. This damage cannot reduce a victim’s Strength score below 0, but anyone reduced to Strength 0 is helpless. Creatures that are affected by this power or that successfully save against it cannot be affected again by the same hag’s horrific appearance for 24 hours. The save DC is Charisma-based.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.