[1] Casiello has written content for three distinct entertainment genres.
He was then hired by WWE, where he served as the creative writer from 2011 to 2016.
[2] In recent years, Casiello has written for Gen-Z Media, where he was head writer for Six Minutes, and its sequel, Six Minutes: Out of Time.
In 2018, Casiello joined the writing team at Respawn Entertainment and was part of the creation of the first seventeen Legends in Apex Legends.
He also co-wrote the book Pathfinder's Quest, with Manny Hagopian and Ashley Reed, as well as the Dark Horse Comics mini-series, Apex Legends: Overtime.