The seventh Doctor started off with amnesia, when he was captured by the Rani in his first story Time and the Rani. In this story he is seen as a spoon-playing, malapropism-spouting clown.
Later in his stories he became a more darker and manipulative Time Lord - nicknamed "Time's Champion".
Links were established linking him to the period of Rassilon and Omega, the founders of Time Lord society. If the series had continued past the 26th season, this theme would have become more prominent. He encountered the Daleks, the Cybermen and the Master in the last televised story of the 26 year run, Survival.
In Dragonfire, he met Ace, a 16 year old "teenager with an attitude", someone content to blow things up with Nitro9: a nitro-glycerine derivative, after a promise to see the galaxy, she joined the Doctor as his companion after Mel left at the end of the story.
He met up with the Brigadier again in Battlefield. Nicholas Courtney, returned to the role and also introduced serveral new characters including a Lady Brigadier in the lead as his character was now retired.
Virgin Publishing produced a range of novels featuring the seventh Doctor, entitled The New Adventures, these full-length novels "take the TARDIS into previously unexplored regions of space and time." The novels originally featured Ace as his companion, but gained a new companions; (Professor) Bernice "Benny" Summerfield, an archaeologist; Roslyn "Roz" Forrester and Christopher Cwej, two Adjudicators from the 30th century joined the 7th Doctor in his travels. These lasted from 1991 to 1999
There are worlds out there where the sky is burning, where the sea's asleep, and the river's dream, people are made of smoke and the cities made of song. Somewhere there's danger, somewhere there's injustice and somewhere else the tea's getting cold. Come on, Ace. We've got work to do
