User blog comment:B214/DxD Zero: Sirzechs story/@comment-2601:8C:601:5692:6089:5245:14CC:C305-20180928184102

So the third chapter is out, and the Jap wiki has been updated with some new info:

The House of Leviathan's trait is「掉尾の海蛇龍」. I'm not clear about the translation, but the three kanji 海蛇龍 translates as "sea", "snake/serpent", and "dragon" respectively. The daughter of Leviathan can apparently transform into such a creature, as implied by her family name. She also possesses top-tier talent and inherent levels of demonic power, able to summon enough water (seawater?) to submerge an entire city through pure demonic power.

Also, the name Vali's father has been revealed: Lazevan/Razevan Lucifer ラゼヴァン・ルシファー. As an aside, I kind of want his mom's name to be revealed to be Rinda リンダ, as it is the Latin form of the name of his namesake's mother in Norse mythology, Rindr.