In the game, there is a spell called Bloodlust, which is named after its predecessor from the third installment. The name used in the spellbook is a matter of Ubisoft's editorial choices, as Nival Interactive was very meticulous and authentic, using names they had already established.
For example, we have a hero named Cristian, who is a specialist in ballistae. In Heroes 3, there was also a Cristian who was a ballista specialist. But here, they decided to rename him Vittorio.
Perhaps the most amusing example is Axel, who is Klaus, who is Sarge.
And yes, don't remind me about "Klaus." I'm already having a heart attack these days, learning that my Axel apparently has a personality disorder...