According to Samael and those who had gone missing for the past two years, they were stuck in this so-called Hell's Gate. It was a powerful ability that only the Grimsbanne originally could wield. Through the years, exceptional vampires were able to achieve a certain level of strength and power and were able to make use of this power.
However, unlike the Grimsbanne Clan, who could naturally unleash such a powerful weapon, many other people out there sought help from another party. These people were greedy enough to exploit others such as Maleficent to gain more power and stand on the same ground as the "cursed" Grimsbanne Clan.
These people's schemes went so far as to seek help from an actual demon.
Yes. A demon.
