The Ni'Var was a 22nd-century Vulcan Suurok-class ship commanded by Captain Sopek, sent in 2151 to remove T'Pol from Enterprise after the loss of the monastery at P'Jem.
The Ni'Var appears in the Enterprise episode Shadows of P'Jem. After the Andorians destroy the Vulcan listening post hidden at P'Jem, the High Command blames T'Pol and Archer for its discovery and orders her recall. The Ni'Var is to collect her once Enterprise has finished a visit to Coridan.
When Archer and T'Pol are taken hostage by Coridanite rebels, Sopek prepares a commando raid that would put their lives at risk, while Trip and Reed work with the Andorian Shran instead. During the fighting T'Pol is wounded shielding Sopek from a shot.
Archer presses the point with the captain afterwards, and Sopek agrees to speak to the High Command on her behalf, so she stays aboard Enterprise.