Strigoi

Strigoi which is Romanian for Vampires is the main Antagonist force of G.I Joe: The Strain (A Future Crossover of G.I Joe: A Real American Hero and The Strain) While they take direct orders from the Master, they also take orders from Eichhorst most of the time. They refuse to take orders from Cobra Commander or any Cobra Subordinates throughout the Invasion of New York.

Strigoi Vipers
The Strigoi Vipers are Cobra Vipers turned by the Master and take orders from the Master as well as Cobra Commander, when the first unit of Cobra Vipers are turned into vampires, in retaliation Cobra Commander in return poisons a unit of Strigoi using a mutated version of Zika and Malaria which both designed by Dr. Mindbender to target and spread to Vampires only. When Thomas finds one of the Strigoi Vipers with a tablet attached, he takes it and returns to meet with the Master.

Upon returning to the Master, Thomas Eichhorst shows the tablet to the Master and the Master plays a recorded message by Cobra Commander, stating directly to the Master. "We had a deal, I'll help you get to New York, as long none of my men are killed or turned into Strigoi after your arrival, for taking a unit of my Cobra Vipers, I have returned the favor by killing them with a mutated strain of Zikia and Malaria. Take this as a friendly warning not to mess with my soldiers-next time the viruses will be released in your chambers." and the video cuts out.