I Thought a Bird can Fly through Mist?

Raven was frustrated, no matter how many times she dived into the thick mist, she could never get through. It seemed as the mist had powers to block all that tried entering it. With a yowl of fury, she pounced on the mist but somehow ended up back on the Dark Forest side. Let me out! Her mind screamed, the words echoed in her head and she tried again, clawing the white cloak with sharp claws and hoping to open up. Why couldn't she get to Starclan? It was just a piece of mist but had stopped her from entering. She collapse on the ground with weariness after hours of attacking the mist with no hope going to the other side.