This looks like a situation where you'd have to kill a couple people, Thalos thought to himself. He stepped back a little. If he took off the mask now, he would be revealed.
There was no way they didn't know the man they had been trying to kill by face, and if not, Dorian would know. He needed a way out of this that didn't lead to bloodshed till the teleportation circle was activated.
Once it was active, all Whispers relays were down, then they couldn't inform the people outside of danger.
"Sir, I was too shocked by your presence to give you proper respect," Thalos dropped to his knees. "Please forgive me. I am just a Stainless, I cannot reveal my face."
Stainless were people that worked among the general population. They weren't fully bought into the mission of the Whitemoon, so they couldn't cast off their mortal ties.
They worked their jobs here then were taken back home secretly. If their real identities were revealed, it could be used against the Whitemoon.