Dämonenpanzer

Demon armors are special magical types of armor. They cannot be worn by mere mortals because they will be cursed and unable to take it off, while the armor completely drains the life energy from them until it ends up killing them. This doesn't pose an issue for undead beings like vampires; it only drains their magical powers. Demon armors are unique. They can be fickle, and may drain magical power from some individuals more than others, depending on their affinity. Either way, they're hard to control and require many years of training before the amount of magical power drain can be reduced to a manageable level.

For this reason, Aras' master considered the cost benefit to be a waste of his time, and never bothered training with it or introducing it to Aras. He just found it out on his own.

And now finally, after years of training in secret, he can make use of a demon armor in battle.