Sylvia didn't know much about the Drocogalla Secret Realm, so Ely wished to know some essential points from the knowledgeable one.
In Klaus's story, everyone knew he was the ninth vampire progenitor, the ancient blood devil. When he reached the very pinnacle of the mortal world's power level, he tried to ascend to the upper realm.
He was prepared to break the realm's restriction wall, but his strength was insufficient. The heavenly tribulation struck him down, and his body crumbled into dust instantly.
He barely saved his soul essence and returned to this secret realm with a soul defect.
For the next several thousand years, he spent his time in a deep slumber on this mountaintop as his resting place. He repaired his damaged soul and was nurtured by the secret realm's spiritual energy, but it was progressing slowly.
Ely asked a few things, but she could only learn about the knowledge from thousands of years ago...
Unlike humans, vampires generally do not eat food for sustenance. They still need blood to survive. Regardless, there are some exceptions as they need nourishments to practice their demonic cultivation arts.