Nacho was a soldier of the Darkbane before entering Slugterra. When Dr. Thaddius Blakk encountered his kind, the Slugterran made a deal with Nacho's master. In trade for use of Dark Water, Blakk would allow Nacho to return with him to Slugterra, disguised as a human. During his time working for Blakk, Nacho has served as a commander of sorts for Blakk's army, as well as a business representative to persuade unwilling partners. After a series of failures, Blakk fired Nacho in favor of his new apprentice, Twist. Nacho was immediately banished back to the Deep Caverns, but he warned Blakk they would meet again. Nacho later snuck back through a portal when the Shane Gang journeyed into the Deep Caverns. Upon returning to Dr. Blakk, Nacho reminded him "Uphold your end of the bargain, or there will be consequences.
You made a deal with my master, and I'm back to make sure you honor it." After his return, Nacho returned to service, working for Dr. Blakk. When Blakk became imprisoned in Stalagmite 17, Nacho broke out Dr. Blakk by creating a temporary portal to the Deep Caverns. In this process, several Darkbane were brought into Slugterra. Nacho disappeared after the defeat of Dr. Blakk, so his current whereabouts are unknown. Most likely, he was sucked back into the Deep Caverns when Blakk's Terraportal was destroyed.
As a Darkbane, Nacho bears tremendous strength, enough to knock a slug out of flight with a single punch. He is dangerous with his blaster, and carries a large arsenal of ghouls at all times. He also has the ability to change his appearance, altering between a human-like form and his natural Darkbane form.