Hiiro no Kakera - 03 - Large 32
Vier (フィーア(meaning 'four' in German and Dutch) is one of the members of the Logos. The only female aide to Aria and the one she trusts the most. Out of all her subordinates Vier was the only one chosen by Aria herself. She is a tactician, like Aria, she is extremely suspicious of Drei.

She disguses herself as Fiona-sensei, an English teacher at Tamaki's school, with blonde hair and blue eyes. She looks like she's of German origin. She also reminds Oomi of his mother.

Upon Oomi's brief defection from the Guardians, she proposed a secret alliance with him to protect Aria and recover the Artifacts but was captured by Drei before she could set the plan in motion. She was then used as a hostage by to ensure that Aria remained loyal to the ideals of the true Logos.

Later on she is revealed to be a homunculus fashioned in the image of Oomi's mother, who was drowned as one of the sacrifices to keep the Onikimaru in check. It is hinted that Drei, who's real identiy is Magus Melchizedek; played a part in her conception.

At the end of the series she is seen leaving the Logos mansion with Aria, never to be seen again.