Eltnum

Eltnum, originally as Sion Eltnam Atlasia ("Eltnum" is a pun on her middle name) is a character originally from the Melty Blood franchise.

She was put into the game as a last minute decision as an original test character for the in-development HD Melty Blood that's been rumored for ages. As a result, she's often the cornerstone of inside references in-between Melty Blood and Under Night In-Birth.