Santo was a male Twi'lek who was present on the planet Tol Ado shortly after the Battle of Yavin. He had a hooked scar over his left brow. Santo worked for a rebel band made up of escapees from the Deathblock and led by the Wookiee Warburton. Unknown to the rest of the rebels, he began cooperating with the Galactic Empire. With his cooperation, the Imperials were able to discover their base in the .
In 0 ABY, Santo was giving information to an Imperial major and the stormtrooper TX-567 when he was encountered by Luke Skywalker, disguised as an Imperial colonel. He did not recognize Skywalker later when he came to the sub-facility searching for help in escaping Tol Ado, but Skywalker identified him due to the moon-shaped scar above his left eye. Warburton ordered Skywalker and his companions, Erling Tredway and Sidney Shortfang to participate in an ambush of Imperial sources to prove that they were not spies, but the battle was a disaster due to Santo's feeding of information to the Imperials. When Warburton wanted to execute Tredway for his poor performance in the fight against the Imperials, Skywalker told the rebels of Santo's cooperation with Imperials. Santo protested, but Warburton had him executed for betraying the group.
Santo was created by Troy Denning and appeared in one of the role-playing strands of the 1990 West End Games role-playing supplement Jedi's Honor. The exact manner in which Skywalker tells the rebels of the sub-facility about Santo's treachery depends on the reader's choices during the battle with the Imperials. If Skywalker allows Erling Tredway to botch the ambush, then Skywalker reveals Santo's treachery directly to Warburton. If he stops Tredway from interfering, then he reveals this information to Tormey, a lieutenant of Warburton. In either case, Santo is discovered and executed by Warburton for treason.