There are several bands known as Katharsis:
1) The most well-known Katharsis (aka KTHRSS) is a German black metal band formed in 1994. The members are Aeshma on "styx" (drums), Scorn on "scythe" (bass, guitars), and Drakh providing "sting" (vocals). The group does not play live shows.

Katharsis has released four full-lengths to date: 2000's 666 via Sombre (later re-released by Norma Evangelium Diaboli on CD) and 2003's Kruzifixxion, 2006's VVorldVVithoutEnd and 2009's Fourth Reich via Norma Evangelium Diaboli. Some of their recent t-shirts were also released by Norma Evangelium Diaboli.

Katharsis has also participated in split releases with Moonblood, Deathcult (Ger), Nhaavah and Black Witchery. Katharsis appeared in multiple compilations, including Black Metal Endsieg I (2001), Black Metal Blitzkrieg (2001) and Tormenting Legends II (2006).
http://www.kthrss.de/

2) A progressive metal band from Romania.The band was formed in 1997 under the name Puls!, in 1998 they changed their name to Katharsis.
The band consists of
Alina Szekely-Maier – vocal
Cătălin Gyulai – guitar
Ovidiu Szekely-Maier – bass
Andras Bilibok – drumms

https://myspace.com/katharsisprogresiv

3) Katharsis are a surf rock band with its origins in New Jersey. In early September of 2008, Justin Chung (Guitar, Lead Vocals) began searching for band members to finish out his desired four piece ensemble. Justin reconnected with his old summer camp friend, Jesse Haack (Drums) who then contacted David McNally (Bass, Back-Up Vocals). Matt Modica, Justin's classmate, originally filled the part of guitarist but scheduling problems eventually led to a lineup change. The band later found Matt Dezenzo, a youthful metal virtuoso, who briefly took over for Matt Modica. However, Justin's songwriting took a turn toward the melodic side and the band eventually parted with Matt Dezenzo. David Scala was then recruited to fill the role of guitarist and lends his unique style to Katharsis' music.

http://www.myspace.com/katharsisnj


4) Katharsis were an alternative/progressive rock band from Greenville, NC that disbanded in early 2007. From the about page on the band's official website: "Katharsis has been a work in progress since 2003. Seeking edgy music with a positive message, guitar players Garett Bissonnette, of One Word, and Patrick Spohr, of Rhetoric, got together to trade riffs and immediately felt they had to passionately pursue the music that unfolded. Settling for anything less than the best was not an option. They auditioned many drummers and bass players before finally finding Cory Granger, a local college student, and Eric Pyburn, Patrick’s bass player from Rhetoric. With the musicians in place, the search for a singer was long and arduous. After two singers came and left, the four members of Katharsis discovered Ean Hirst, of Seraphin, running sound at a local bar. As soon as they heard his voice they knew they had found their front man. With the ensemble complete, they immediately started an intense writing session.

The band had been writing and rehearsing with and without singers over the previous year and a half before finding Ean. Combining the original melodies created by Katharsis and the lyrics written by Ean, Katharsis is brings a new sound to rock music, fusing the best of every world and never settling for anything that doesn’t live up to the title of being “cathartic”. A unique musical style, complete with vocals reminiscent of Alice in Chains, a melodic feel on par with A Perfect Circle, and the overall catchiness of Incubus, sets the stage for Katharsis’ powerful positive message."

http://www.katharsisrock.com/index.htm

5) Katharsis are Daniel Malson, Jano Sanguine, Rick Sanford, Tim Vickers. Experimental/industrial quartet from San Francisco. Nothing else but this is information is known. Read more on Last.fm. User-contributed text is available under the Creative Commons By-SA License; additional terms may apply.