One of your squad emmbers that also happend to be a krogan bounty hunter and one of the last Krogan Battlemasters. Wrex was deadly concered for the future of the Krogan and the genophage.
Wrex first served with other Krogan and influenced many Krogan to focus on breeding for just one generation. However, his father Urdnot Jarrod did not like the idea and invited Wrex to a crush. Wrex knew it was a trap but, knew it was sacred and would go against tradition not to. When Wrex didn't agree with Jarrod his father signaled his men to atatck and they killed Wrex's warriors. Wrex managed to escaped and kill his father.
Wrex serevd Commander Shepard and could possibly die in the Virmire mission. Howeevr, if he survives he becomes the Urdot leader by Mass Effect 2. He also welcomes grunt to his clan by Mass Effect 2. By Mass Effect 3 Wrex will be Commander's Shepard's ally and his fate can vary. In Shaperd choses to sabotage the genphage Wrex will take on Commander Sheaperd in a shoot out and can either be killed by Commander Shepard or Comamnder Bailey.