Across season 3 of Breaking Bad we see an enigmatic pair of recurring minor characters I've dubbed the Murder Twins. They are twin brothers Leonel and Marco Salamanca, played by real-life brothers Daniel and Luis Moncada. (The brothers are not twins in real life. Luis is 3 years older than Daniel and about 2 inches taller.) They have tattoos and wear clothes that practically scream "drug gang member" but they hardly ever speak. They move with creepy mechanical precision. And they are not reluctant to employ violence.
The Murder Twins are also known by fans as The Cousins. They are cousins of slain gang boss Tuco Salamanca and nephews of injured former gang boss Hector Salamanca.
The Murder Twins appear in the cold open sequence of the season 3 opener. People in an impoverished Mexican village are crawling on hands and knees up a dirt road. The Murder Twins arrive in an expensive Mercedes car. The twins join the villagers on their hands and knees. They enter a shrine to Santa Muerte- which totally means Death Santa, by the way- where one places a donation and the other places a pencil sketch of Walter White. This is an offering to Death Santa. 🎵 He knows whether you've been bad or good, and he doesn't care; he's going to kill you either way. 🎵
Later in S3E1 the Murder Twins drive to a small primitive farmhouse where laundry is hanging on a clothesline. They strip off their clothes, with the family watching, and take the clothes from the line.
The impoverished family is terrified by their looks and by the guns visible when they take off their jackets. Once they've changed their looks- except for their bespoke boots- they leave the key to their luxury car and walk away.
Finally in S1E3 the Murder Twins are sitting in a hay truck, being smuggled across the US border. One of the other smuggled immigrants tries striking up an appearance about their appearance- and stops after he notes the silver skulls on the tips of their boots, realizing he's just called everyone's attention to their gang symbols. The Murder Twins pull out their guns and murder everyone in the truck, at least half a dozen people. Then they light the truck on fire and walk away.