Though a great warrior and leader among his people (the brutal and mirthless Tharks) he possesses a sense of compassion and empathy uncharacteristic of his race.
In t A Princess of Mars, with the help of the newly arrived earth man John Carter he becomes a Jeddak (king) of the Tharks.
Tars Tarkas is the very first Barsoomian encountered by John Carter when he appears on Mars. In fact, Tars Tarkas begins by making a very earnest attempt to kill Carter, having discovered the Earth man inspecting the Tharks’ incubator (in which the tribe’s precious eggs are sealed up for five years prior to hatching). The attempt fails, and Tars Tarkas instead takes Carter prisoner and transports him back to the nearby dead city in which a group of Tharks have taken up temporary residence. John Carter kills one of the Tharks in a fight and finds that he has not only won a victory over an enemy but gained his victim’s rank and possessions as well.
Over the course of the next weeks, Carter discovers the character of the green Martians, and comes to respect Tars Tarkas for his abilities as a warrior and statesman. More than that, Carter discovers that Tars Tarkas has a secret: long ago he committed the great sin (for a green Martian) of falling in love and, worse, had a child (egg) with his lover, Gozava. Tars Tarkas and Gozava hid the egg and incubated it in secret. But Tars Tarkas was ordered away on a long military expedition, and when the child finally hatched, Gozava managed to mingle her child with the returning children from the communal incubator. But Gozava’s maternity (although not the child’s identity) was discovered, and she was tortured and killed by the Tharkian chieftain Tal Hajus for the crime of child bearing. However, even under torture she refused to reveal the name of the child’s father. The daughter’s name is Sola, and she befriends Carter and tells him the story of her birth and the identity of her father.
When he learns this, Carter’s sympathy and admiration for Tars Tarkas increases, and he resolves to do all he can to help the Thark. Over time, the two become friends, and Carter, after escaping the Tharks in the course of his pursuit of Dejah Thoris, returns to them and helps engineer a duel between Tars Tarkas and the Jeddak of Thark. Tars Tarkas wins the duel, and according to Tharkian law becomes Jeddak. Thereafter, Tars Tarkas becomes one of John Carter’s closest allies, and appears in a number of the other novels in the series.