Vampires were known as one of the strongest races even among the Pillars, for several reasons. They were strong physically, second only to Axalts and Ashens, their magical abilities were also top-notch, but all of this was only secondary effects.
The most important of course was their regeneration, as well as quickly becoming stronger and replenishing energy with the blood of other creatures. Of course, vampires had natural enemies, the most famous of which were Ashens.
A Vampire could easily drink the blood of an Elf or Demon, but if a Vampire tried to do the same with an Ashen, it would be a deadly mistake. The flames would simply burn the Vampire leaving him no chance of survival.
It was also one of the reasons why Alucard and Gael's friendship was so strange and in some parts even ironic. Vampires and Ashens were not open enemies, but the peculiarities of their races prevented them from being allies.