The Student Council members, and a handful of other characters, from the anime Revolutionary Girl Utena. These duelists fight for possession of the Rose Bride (Himemiya Anthy) and the mysterious power believed to accompany her.
Each duelist seems to have a particular reason to get this "power to revolutionize the world"—Miki wants his "shining thing," the feeling of his twin sister's piano playing from long ago; Juri wants the power of miracles so things will work out between her and her unrequited love interest (poor Juri); Saionji wants "something eternal"; the Black Rose duelists have their own little thing going on; and Utena herself just wants Anthy to be freed from her destiny as Rose Bride. Oh yes, and Touga just wants power.
All duelists are identified by the Rose Signet, a ring bearing the rose crest of Ohtori Academy. The duels are fought in an arena behind the school, but the real nifty bit is the special advantage that the current victor of the duels gets- the Sword of Dios, which is a semi-magical sword that can be conveniently extracted from the rose bride's chest. This changes a bit as the series goes on, but then again, so does just about everything in this show.