Antonio "Tony" Ruiz was a human male alive in the mid 22nd century. A native of Cuba, Ruiz came to Sauria as a mining engineer and stayed on as a medic after plague struck the area of the planet he was working in, and later became a freedom fighter and fought alongside the Saurians to depose the tyrant Maltuvis.
In 2164 Ruiz met Charles Tucker III, who had traveled to Sauria on a Section 31 mission using the identity of Albert "Al" Sims. Because the two were originally from fairly close geographic areas and were both affected by the Xindi attack of 2153 the two became friends.
When Maltuvis began moving to take control of the entire planet, Tucker was ordered to return to Federation space by his superior Matthew Harris. Ruiz also was ordered to leave, however he decided to remain and fight Maltuvis. When Tucker tried to remind Ruiz that he was one man, Ruiz quoted Fidel Castro in saying, "It does not matter how small you are if you have faith and plan of action!" The argument ended with Ruiz angrily punching Tucker, who promptly left, feeling himself no longer worthy to call himself Ruiz's friend. (ENT - Rise of the Federation novel: Tower of Babel)
He stayed behind on Sauria, aiding the resistance against Maltuvis for the next year and a half. Eventually, he managed to record the destroction of the Lyaksti capital city, and transmit the recording off-world. The news of this atrocity forced the Federation Council to intervine on behalf of the people of Sauria and sent a team of Starfleet military advisors.
Not long after, Albert Sims returned to the planet with a plan to cut off Maltuvis's off-world support from the Orion Syndicate and bring down his bosses at Section 31. To enlist his aid and re-earn his trust, Sims revealed his true identity as Charles Tucker III to Ruiz. In the course of their mission the pair was captured by Maltuvis's forces, and during their escape the wounded Ruiz sacrificed his life to buy time for Tucker to evade their pursuers. (ENT - Rise of the Federation novel: Patterns of Interference)