As the Cardinal reached near the barrier that had been shrouding the city, he brought a token out of his pocket.
The token started shining with the same aura as the barrier. An opening appeared in the barrier, large enough for the Pegasus to easily pass.
The Cardinal left the city through the opening in the barrier with Eren following closely behind.
As the Holy Emperor, Eren also had a token of his own that could create an opening in the barrier. If anything, his pass had even more authority than the Cardinal, albeit not as much as the Holy Priestess had.
After he and Eren passed through the hole in the barrier, it closed and the Holy City was sealed again.
Eren had experienced flying in the sky. He even rode a Phoenix, but the experience of rising a Pegasus was quite unique in itself.