Mass Effect has a long history with the Krogan race, so it was only natural to expect the Pathfinder would find themselves with a powerful Krogan squadmate and ally after arriving in Andromeda. No one actually expected that Krogan to be one of the oldest, most experienced, grizzled and crotchety Krogan in the universe.
Nakmor Drack's age wasn't a deterrent to his abilities, however. Drack spent nearly a millennia and a half kicking asses all over the Milky Way, so when his people joined the Andromeda Initiative, going along for the ride felt like the only natural thing for him to do. Finding new things to shoot in a brand new galaxy where the Krogan could escape the prejudice and, hopefully, the genophage, seemed like the only smart move for a lot of Krogan, including Drack.
If one considers the centuries the people of the Andromeda Initiative spent sleeping, Drack was well past two thousand years old when he arrived in the Heleus cluster. His extensive battle history, which included time as a soldier, mercenary and even a pirate, took a heavy toll on his body, and he had the prosthetic limbs and synthetic organ replacements to prove it.
Descended from the famed female Krogan warlord of the Rebellions, Shiagur, Drack was relatively young when the Krogan Rebellions began. In conversations with the Pathfinder, he claimed that his krantt could credit over two hundred kills during the battles, among them at least three of the council's Spectres. After centuries of fighting his way through the Milky Way, Drack eventually decided he'd like to see at least one more horizon before he met his end, and he traveled with his clan, including his granddaughter Kesh, to Andromeda.
During the uprising on the Nexus, Drack was woken alongside Nakmor clan leader Morda to help put down the rebellion. Juran Tann promised the Krogan a seat on the council if they stopped the rebellion. In the end, the uprising was likely only staunched because of the Krogan's aid. When all was said and done, Drack and Morda met with Nexus leadership to claim their council seat, but Juran Tann went back on his word. Denying the Krogan representation in political affairs created further tension between Clan Nakmor and the other alien species.
Clan Nakmor still had to deal with the Andromeda Initiative regardless, so Morda appointed Kesh as her ambassador to the Nexus and the clan left to forge their own way in the galaxy. Drack also left the Nexus after the rebellion. While Clan Nakmor made themselves busy founding the Krogan colony of New Tuchanka on Elaadan, Drack did his part to protect the colony by taking out as many Kett as he could find.
He was so disenfranchised with the Initiative after their treatment of the Krogan that when he happened upon Pathfinder Ryder at the Kett base on Eos, Drack treated them with distrust. He refused to join their party at that time, claiming the day he had anything to do with the Andromeda Initiative would be the day "the clouds part and the Kett keel over."
Later, Pathfinder Ryder came to Drack's rescue on Eos after activating the Remnant vault and parting the clouds in the sky. Showing up and helping him take out the Kett, Drack was so impressed with Ryder's actions, he relented to joining them on the Tempest and helping them with their mission going forward.
Drack and fellow squadmate Vetra shared a close bond, with the Krogan seemingly looking out for the Turian as if she were one of his own. The pair had a history together in underground dealings. At times, they tended to business together without involving the Pathfinder to keep their leader's nose clean when engaging in shady transactions.
Despite his overwhelming ability to destroy enemies, Drack's body was old and tired, and the numerous synthetic limbs and organs that kept him functioning didn't seem as though they'd be enough to keep the Krogan going much longer. After completing Drack's loyalty mission, the Pathfinder received an email from Kesh, asking them to take care of her grandfather. Ryder visited Drack in the med bay, where they discovered that several of his redundant organs were beginning to fail.
Like most Krogan, Drack had no intention of allowing old age to be the thing that took him out. When Ryder spoke with Drack about what was going on with his body, he shared with them the deep depression that overcame him after he originally received his implants and prosthetics. He felt purposeless, ineffectual and saw no future for himself, but then Kesh was born. Holding her in his arms, the shaman who handed Kesh to him told Drack that she was likely going to die, and suddenly he felt a renewed purpose. He picked the pieces of his life back up and lived from that day forward for his granddaughter.
After losing their father on Habitat 7, Ryder could take comfort in Drack's presence and strength. Despite the differences in their species, Drack looked out for the Pathfinder with the same dedication he had for his own granddaughter if they managed to win him over. In true Krogan spirit, Drack never let his infirmities hinder him from fighting his way through Andromeda in the hopes of paving the way to a more peaceful future for his people, his granddaughter and the clutch of eggs she produced.