The Story of Trista:

Well, Sailor Pluto appears at the end of SMR. She is a very secretive girl. In teenage counting she's about 18 years old. Not for real though. For real she's thousands of years old. Trista only appears 18 because she can control time. She owns one of the 3 talisman to make the holy grail. The Garnet Orb. A very powerful object used, I think, in all her powers.

Sailor Pluto's Powers

I haven't actually seen any of these powers yet because I live in Canada, so I'll just give an answer except I'll rephrase it in my own words.

*SMS Powers*

*Pluto Planet Power!*
Trista says this to transform into Sailor Pluto.
*Dead Scream*
Sailor Pluto whispers this and her staff twirls around in a cloud, she grabs it and a purple blast comes out of her staff. (Thank you to Setsuna X for telling me that Sailor Pluto doesn't scream Dead Scream but she whispers it. Thanks!)(She should scream it. It's called Dead Scream!)
*Dark Dome Close*
This phrase closes the power to travel in time space.

*SMSSS Powers*

*Pluto Crystal Power!*
Trista says this to transform into Super Sailor Pluto.

Sailor Pluto
Super Sailor Pluto
Trista