Gatekeeper duty had been rather uneventful for Castiel, however he enjoyed taking the opportunity to get to know Diana. He found talking with her pleasant and was about to ask another question when energy from the portal spiked. The new arrival stunned Castiel momentarily as it wasn't a regular sight to see a man flying. But he had bare witness to many strange and wonderful things so he wasn't sure why he was so surprised.
"We can answer that." Castiel said by way of greeting, head tilting slightly as he looked up to the flying man. He did seem like he was a threat, just lost like the rest of them upon arrival.