“For the same reason that Viktor never conspired against Marcus: Fear....” – Tanis, Underworld: Evolution ... Movie Quotes Database

Tanis

(Answering Selene's next question)

For the same reason that Viktor never conspired against Marcus: Fear. He was warned that should Marcus ever killed... all those in his bloodline would follow him to the grave.

More from Underworld: Evolution

Tanis Yes. Yes, a clever deception... but one Viktor was hardly willing to put to the test. And so Marcus was protected... at all costs. Tanis You should know. It's William's Prison. The prison your Father was commissioned to build. Tanis The Winter of Lucian's Escape. Your Father knew too much. Or too much for Viktor to risk... especially when Lucian... had the key, (holds up Sonja's Pendent,) to William's cell.