Urdnot Wrex

Urdnot Wrex was a famed krogan mercenary, bounty hunter, and one of the last krogan battlemasters, rare warriors who combined powerful biotics with heavy firepower. Long-lived even by the measure of his people, he had heard of Commander Shepard through his travels and came to respect the Commander as a fellow warrior. Despite a life spent killing for credits, Wrex was among the few krogan who looked past the rage of his species toward a future, and he became one of the most consequential figures of his age, a clan leader who held the fate of the krogan in his hands. (Mass Effect; Mass Effect 2; Mass Effect 3)

A leader who turned away#

Born into Clan Urdnot, Wrex earned fame young, killing a thresher maw during his Rite of Passage, a feat almost never achieved, and becoming the leader of a smaller Urdnot tribe while still a youth. After the Krogan Rebellions ended and the genophage left the krogan unable to replenish their numbers, most clans wanted to keep fighting. The loudest voice for renewed war was Wrex's own father, the warlord Jarrod. (Mass Effect; Mass Effect 2)

Wrex disagreed. He argued that the krogan lacked the numbers to win and could not breed quickly enough to recover their losses, and he urged the clans to turn to rebuilding instead. As his ideas spread, Jarrod arranged a Crush, a meeting on neutral ground, in the sacred burial grounds called the Hollows. Sensing a trap, Wrex came anyway, and when Jarrod's men sprang their ambush they cut down Wrex's warriors. Wrex escaped, but not before driving his knife into his father. The betrayal opened his eyes to a hard truth, that most krogan would sooner die in battle than rebuild, and he left his people behind to spend three centuries serving no master but himself. (Mass Effect)

With Shepard against Saren#

Wrex first crossed paths with Commander Shepard on the Citadel, where he had been hired by the Shadow Broker to kill the criminal Fist. He remained with Shepard afterward, drawn by the gathering storm around Saren Arterius. Aboard the Normandy he kept his own counsel, blunt and rarely roused to anger, though terrifying when he was. He respected the biotics among the crew and held the usual krogan disdain for turians and salarians. (Mass Effect)

On the planet Virmire, Shepard's team discovered that Saren might have found a cure for the genophage and was breeding a krogan army. The salarian special forces planned to destroy the facility, and if Wrex was present he was enraged, believing the cure could save his species. The confrontation could end in different ways. If Shepard could not reason with him, Wrex was shot and killed; otherwise he accepted that Saren intended only to enslave the krogan, stood down, and turned his fury on Saren instead. Whether he lived through Virmire would shape everything that followed. (Mass Effect)

Leader of Clan Urdnot#

By 2185 Wrex, if he had survived, was the leader of Clan Urdnot, having returned to Tuchanka to unite the clans using the victory on Virmire as a rallying point. He instituted reforms, offered protection to fertile females in exchange for loyalty, and faced opposition from traditionalists. If Wrex had died on Virmire, his broodbrother Urdnot Wreav held the clan instead, a cruder and more vengeful figure. When asked to rejoin Shepard, Wrex declined, needing to keep the clans united. (Mass Effect 2)

The genophage cure#

During the Reaper War, the krogan leader was called to negotiate an alliance with the turians and salarians, and Wrex demanded that the genophage be cured as his price. He revealed the existence of fertile krogan females being held on the salarian world of Sur'Kesh, survivors of brutal experiments, and the effort to recover them and develop a cure became one of the war's defining campaigns. The salarian doctor leading the work was central to it, and Wrex's trust in Shepard rose or fell depending on whether the Commander had preserved earlier cure research. (Mass Effect 3)

The salarian leadership secretly offered Shepard a deal: sabotage the cure in exchange for salarian support. On Tuchanka, as the clans gathered and a Reaper guarded the curing facility known as the Shroud, the female krogan called Eve and the doctor worked to finish the cure while the krogan summoned the great thresher maw Kalros to bring the Reaper down. The outcome depended entirely on Shepard. If the cure was genuine, Wrex saw his people set on the path to rebirth and threw the krogan into the war, vowing to focus on rebuilding rather than revenge. (Mass Effect 3)

If the cure was sabotaged and the deception went undiscovered, Wrex believed the krogan cured while the "cure" was a fake. If he learned the truth, he confronted Shepard on the Citadel in a rage, and the encounter ended in his death, after which the krogan withdrew their support and hunkered down on Tuchanka. In the accounts where the cure was real and Wrex lived to the war's end, he was seen rallying his people for the battle on Earth, looking ahead to a resurgent krogan future and naming Shepard a hero to every krogan born thereafter. (Mass Effect 3)