The Sea God of the Greek Celestial Court, Poseidon, and the Lord of the Underworld, Hades, indeed quickly followed suit right after their Divine King, Zeus, and hurried to Demon City where the assembly of gods was taking place.
These two formidable chiefs of the Western Divine Court arrived in Demon City almost as swiftly as Zeus and the Lord of the Nordic Pantheon, Odin.
However, all four of these divine staves chose to... keep a low profile.
To be honest, their actions this time could all be considered as sneaking in, which certainly wasn't a lawful act. The main reason being, they had not notified Mr. Jade Emperor, the Heavenly God Yu Siang of the Eastern Celestial Court, in advance.
After all, Demon City was also under the jurisdiction of the Eastern Celestial Court. Ay ya.
The reason they didn't notify in advance was not to surprise Empress Shangguan Linlang, but rather to create... thrills and scares.