Blitz was a Clone ARC Commander in Rancor Battalion. They, along with fellow ARC Commander Colt and ARC Commander Havoc, oversaw clone trooper training during the Clone Wars.
ARC trooper Commander Blitz
Blitz like all clones was created on the aquatic planet of Kamino, from the DNA of the late bounty hunter Jango Fett. During the Clone Wars they served as an ARC trooper with the military rank of Clone Commander, and was placed in Rancor Battalion. During the Clone Wars, they were stationed on Kamino and oversaw clone trooper training with ARC Commanders Colt, Havoc, and Hammer. They later participated in the Battle of Kamino, and when Separatist Trident drills attacked, they led three Advanced Recon Force Scout Troopers to destroy them. Blitz and Hammer were the only survivors of the few ARCs that participated in the battle.
Blitz first appeared in the episode "Clone Cadets," albeit unidentified. They were first identified in the new Star Wars canon, on the card Clone ARC Commander Blitz, released as part of the Rank & File set on the Star Wars: Card Trader app in 2018. In the Legends continuity, they were first identified by the Star Wars: The Clone Wars toy line set Defend Kamino.