There is an old saying to threaten those who commit cold-blooded crimes - an eye for an eye, blood for blood. This saying gives meaning to revenge and encourages motivation to repay unwanted debts.
One extraordinary ability of the Spellfire world was named exactly like this old saying - Blood for Blood. It is a rare blood ability that increases strength, speed, and stamina. Although the effect is temporary, it gives you an advantage over your opponents.
Legend has it that this ability was passed down through the generations of powerful vampire families. That's why it is not publicly known.
This ability is tough to control, and only the most potent vampires can use it without consequences. When this ability is activated, the vampire's eyes turn red. After that, the vampire becomes incredibly aggressive and strong.
In some cases, vampires who use this ability for too long lose their minds and become mindless killing machines. So it's best to be very wise while using this ability.