Doing Classic Monsters Good: Medusa

Medusas

HD: 2*

AC: 12

Movement: Pedestrian

Attacks: Seething mass of snakes on her head can lash out and strike within arm's reach, dealing 1d4 and forcing a Save vs. Poison; -4 to Hit against armored opponents. Otherwise, as an ordinary human, using whatever tools she has available.

Special: Those who gaze upon the Medusa must Save vs. Petrification. This process begins as paralysis—particularly in the face and eye muscles, preventing manual operation of the eyelids—and takes 2 rounds. If line-of-sight is interrupted in the first round, the victim is restored to mobility within an exploration turn; if in the second round, they remain paralyzed until washed in spring or river water.

Behavior & Notes: The primary change or refinement here is to not turn her into a tank. The interesting thing with the Medusa is that when you realize you're up against a Medusa you're basically in a standoff position where you can't risk opening your eyes and so are limited by blindness and the resultant difficulty of coordinating, but if you stay in formation and prepare to strike anything that approaches then the Medusa can't really risk getting into weapons range. Giving her a boatload of HD as D&Ds tend to do kind of breaks this symmetry and gives the Medusa little reason to avoid close combat, which removes the most interesting part of her, which is that she's very old and very cunning and very tragic, and she knows this, and knows how to manipulate would-be heroes. 

She's also very aware of the fact that many are under the impression that her petrification only takes effect on eye contact, and will happily exploit this fact.

The mirror trick works, but she's wary of it. She will often carry bottles of ink, smoking censers, or blindfolds to counter mirror attacks. In fact, she will often strategically position mirror emplacements in her lair to project her image from afar, allowing her to petrify without putting herself in harm's way. 

A Medusa is a person-type monster, meaning she's a person. She could probably learn to become a Fighter-type or, Buddha help us all, a Magic-User. You know, it would actually kind of make sense for Projected Image to be a 6th-level spell if that image also petrified people.