As the two were speaking, they saw off to one side a pair of blue-clad boys bearing pennants and a jeweled canopy, who called aloud, 'King Yama requests you — requests you!'

Summons by page-boy. The 青衣童子 are blue-robed attendant boys of the infernal court — 子 here is zǐ, the full noun. They carry 幢幡, ceremonial pennants, and a 寶蓋, a jewelled canopy of state. Everything about the invitation is court protocol; only the address is unusual.

So Taizong, together with Magistrate Cui and the two boys, stepped forward. All at once he saw a walled city, above whose gate hung a great placard inscribed with seven large golden characters: 'GATE OF GHOSTS, NETHER REGION OF SHADOWY GLOOM.'

The sign over the gate reads 幽冥地府鬼門關 — "Gate of Ghosts, Nether Offices of the Shadowy Dark" — in seven large gold characters, and Chinese has used 鬼門關 ever since for any point of no return; to have "passed the Gate of Ghosts" is to have very nearly died. 掛著 and 寫著 both use zhe, the little marker that holds an action in place: hanging there, written there.

The blue-clad boys shook their pennants and led Taizong straight into the city, walking on down the street.

The 將 here is jiāng, doing the job English does with word order — it picks up the object and puts it in front of the verb: took the pennants and shook them. 中 is zhōng, "within."

Then he saw, at the roadside, his late father Li Yuan, his late elder brother Jiancheng, and his dead younger brother Yuanji, who came forward crying, 'Shimin has come! Shimin has come!'

And here the chapter stops being about a dragon. Waiting at the roadside are 李淵, Lǐ Yuān, the emperor's father; 建成, the crown prince, and 元吉, the younger brother — the two men Taizong had killed at the Xuanwu Gate in 626 to take the throne. 世民 is his personal name, Lǐ Shìmín. Nobody in hell calls him Your Majesty.

Jiancheng and Yuanji rushed up to seize and beat him, demanding his life. Taizong could not dodge in time and was clutched fast in their grip.

索命, "to demand a life back," is what a murdered ghost does; the phrase is still the standard one for a vengeful spirit. The killings that made Taizong emperor arrive to collect on the threshold of the court that will judge him, and he cannot dodge fast enough.

By good fortune Magistrate Cui summoned a demon-runner with blue face and jutting fangs, who with a single shout drove Jiancheng and Yuanji back, so that Taizong won free and went on.

青面獠牙, "blue face and jutting fangs," is the stock description of an infernal enforcer, and still a live idiom for anything hideous. 喝退 is to drive someone back by shouting at them. The emperor is rescued from his own brothers by a demon, on the magistrate's orders — the first favour of many.

Before he had gone a few li, he came upon a tower-hall roofed in jade-green tiles, truly magnificent. Thus it appeared:

碧瓦樓臺 is a hall roofed in kingfisher-green tile. The tag 但見, "and this is what he saw," is the storyteller's cue for a descriptive set-piece in verse.