User blog comment:DivineHalo/Mirajane's takeovers (72 in total?)/@comment-5147941-20120630192147

According to someone who was able to translate the page with mira's filler arc form on it they confirmed that it is called 'Satan Soul: Halphas.

The scan reveals the name of Mira's new form:

Satan Soul: Halphas (ハルファス)

Halphas, also known as Malphus or "Count Malphus," is the 38th ranked demon among the 72 demons featured in Ars Goetia in the Lesser Key of Solomon. Sitri, another one of her forms introduced in the manga, is ranked 12th as "Prince Sitri." So it seems Mira's "primary" Satan Soul form may also be named after one of these demons.