Call-Back: While the triplets weren't around for the Red Death, they recognize the Purple Death's resemblance to it from depictions of it their parents made.
Killed Offscreen: Apparently Drago had the Screaming Death killed by his Bewilderbeast, though it's vague if it was a Screaming Death or the same one the Madrigals faced years prior.
Drago darkly says "I believe in learning on the job..." when he brings Karla and Pedro with him on a mission.
The "challenger" the Northern Alliance finds is a Purple Death, an alpha-species that only appeared in the Dragons: Riders of Berk comic book tie-in from Titan Comics.
Shoot the Messenger: When any of his soldiers rightly point out that Karla and Pedro are too small, too inexperienced and not thoroughly brainwashed enough for field work, Drago responds by breaking their bones, giving them bruises and leaving them with "not as many fingers as they'd like."
