Much like Eli Shane, Tad is from The Surface and took a drop down to SlugTerra with his slug Pieper. The Shane Gang take Tad under their wing, training him to blast like a pro with Eli's old blaster and teaching him to live by the Slugslinger's code. Tad takes to it like a natural, and as Kord says, it looks like they have another "slugslinging savant from the Surface" on their hands.