Hotaru is the most mysterious Senshi, and the most powerful (besides Sailor Moon).  She can destroy the world in one word or two.
    Her storyline is quite interesting, and a little confusing (to me anyway).  She appears quite weak, but that's because she has the power to heal (which most people think is gross).  She doesn't have any friends because of her healing powers, but her best friend is Rini (Chibi Moon).
    She appears last in the series.  Her mother, Keiko Tamoe, was killed in a lab accident, and was possessed by Mistress 9. Her only parent is her father, Professor Souichi Tomoe, who becomes the assistant for Mistress 9 and makes monsters and such to get rid of the Sailor Scouts and get the Holy Grail.
    Now, here comes the confusing part.  Hotaru was reborn as a baby at the end of the Sailor Moon S series, and appeared as a baby at the start of the Sailor Stars series. Then she gave Uranus, Neptune, and Pluto their power-ups. She grew fast, being a 4-year-old child by the end of the first episode, and her "regular" age after the second episode. Pretty far-fetched.
    To add to this story line,  the Outer Senshi wanted to kill Hotaru because Sailor Neptune had a vision about Hotaru destroying the world.  The Inner Senshi refused to aide them, and instead protected Hotaru because Hotaru was Rini's best friend.  This caused a lot of conflict between the Senshii.
    Anyway, once it all said an done, Hotaru became Sailor Saturn after destroying Mistress 9.  There you have it, the very short version of Hotaru's life story. :o)

BASIC INFORMATION

Name: Hotaru Tomoe
Birthday: January 6
Blood Type: AB
Astrological Sign: Capricorn
Favorite Color: Purple
Favorite Gemstone: Fluorite
Hobby: Collecting Lamps
Favorite Food: Nihon Soba
Least Favorite Food: Milk
Favorite Subject: World History
Least Favorite Subject: Physical Education
Has Trouble With: Marathons
Strong Point: Injury Treatment
Dream: To be a doctor

ATTACKS

Silence Wall:
Sailor Saturn's attack, used to block other attacks or abjects being thrown at her. 
Silence Glaive Surprise:
This attack was used in Sailor Stars episode 6. It releases death, but Saturn dies also is she uses this power.
Death Ribbon Revolution:
Sailor Saturn's attack to destroy the world.