"I just... I really want to kill a Primarch!"[1]
Clancy is an Imperial Navy menial of the Imperial cruiser Marbo's Glutes. He is the main antagonist of the Bro:Trip Tale of Two Primarchs spin off.
TTS Canon
Clancy is a very polite and well-liked servant who was aboard the Imperial cruiser carrying Vulkan and Corvus Corax. However, he betrayed everybody by crashing the ship, stating that it was always his dream to kill a Primarch. When most of the crew survived, including himself, he was nearly executed, until he revealed that his friends in orbit were about to drop an Exterminatus missile on the planet that they were on. During the confusion, Clancy managed to escape.[1]
It is possible that Clancy is an agent of Chaos, though this is unclear. Clancy insists that he serves no one.[1] Instead, he appears to easily befriend anyone he encounters and manipulating them into doing his bidding; he was even able to get the Jopallian planetary governor, Lance Cashpants, on his side with a mere BBQ sauce sandwich, then use his newfound power to ensure that Vulkan would die of his infection by preventing the Astartes from obtaining medical treatment.[2]