Lepus

Vier is one of the twelve Dark Warlords.

In Fire Emblem: Seisen no Keifu, little is said about the Dark Warlords, but they are all fought in the Final Chapter near Barhara and eventually defeated, including Vier. Vier is not fought in Fire Emblem: Thracia 776.

Like all of the other Dark Warlords, Vier's name is a German number, in this case it is four.

In-Game
Possessing no weapon, kill Vier anyway you like. However, she has a Fortify Staff, so she should be killed before you go after the other Dark Warlords so she won't heal her comrades.

Base Stats
|High Priest |None |30 |80 |13 |25 |22 |21 |4 |16 |21 |5 |0 |3000 |Life Prayer |Staff - A Fire - C Thunder - C Wind - C |Fortify

Kakusei
|Battle Cleric |15 |53 |26 |21 |20 |24 |23 |20 |22 |6 |Renewal |? |Brave Axe Recover