現了本像 He Shows His True Form
他兩個往往來來，鬥經三十餘合，不分勝負。豬八戒立在山前，見他們戰到甜美之處，舉著釘鈀，從妖精背後一築。原來那怪九個頭，轉轉都是眼睛，看得明白。見八戒在背後來時，即使鏟鐏架著釘鈀，鏟頭抵著鐵棒。又耐戰五七合，擋不得前後齊掄，他卻打個滾，騰空跳起，現了本像，乃是一個九頭蟲。觀其形像十分惡，見此身模怕殺人。他两个往往来来，斗经三十余合，不分胜负。猪八戒立在山前，见他们战到甜美之处，举着钉钯，从妖精背后一筑。原来那怪九个头，转转都是眼睛，看得明白。见八戒在背后来时，即使铲鐏架着钉钯，铲头抵着铁棒。又耐战五七合，挡不得前后齐抡，他却打个滚，腾空跳起，现了本像，乃是一个九头虫。观其形像十分恶，见此身模怕杀人。
逐句解 Line by line
The two of them went at it back and forth, fought through thirty bouts and more, and neither won nor lost.
分 is fēn, to divide or distinguish, so 不分勝負 is that no distinction of winner and loser appeared. 不 keeps bù before the level 分. 合 counts bouts of combat, as it did at 交戰三合 earlier in the chapter, and stays at hé.
Zhu Eight Rules stood before the mountain, and seeing them come to the sweetest part of the fight, raised his nine-tined rake and drove it in at the fiend's back.
處 at 甜美之處 is chù, a point rather than a place — the point at which a thing is at its sweetest. 舉著 takes the durative 著 zhe, 背 is bèi, and 鈀 stands at pá by the corpus-wide ruling. 一築 takes 一 at yí before the falling 築 zhù.
But it turned out that the fiend's nine heads had eyes all the way round, and he saw it plainly.
看得明白 takes 得 at de, the linking reading: 明白 is a complement stating how the looking came out, and nothing is obtained. 看 is kàn, to look, not the kān of keeping watch, and 都 is dōu. 原來 marks the narrator turning back to explain what the reader could not have known.
Seeing Eight Rules coming up behind, he used the butt of the spade to fend off the rake while the head of it held off the iron cudgel.
Both 著 are the durative zhe and both specs are supplied by position. 鐏 is the metal ferrule on the butt of a shafted weapon, the end opposite the blade, so the line has him using one implement at both ends at once. 背 is bèi.
He held out another five bouts or seven, but could not fend off the swinging from before and behind at once; so he took a roll, sprang up into the air, and showed his true form — which was a Nine-Headed Worm.
擋不得 takes 得 at de: V不得 is the potential negative, cannot-be-done. 不 keeps bù, since the spec lowers 得 to a neutral syllable rather than raising it. 五七合 is the vernacular five-or-seven, an unspecified handful, and 掄 stands at lūn by the corpus-wide ruling.
To look upon its shape was to see something wholly hideous; to behold this form was to be frightened to death.
⚠ This is a seven-graph couplet printed as prose. The line it sits on carries no verse marker in the source, so it is authored as prose and stays in a three-panel passage; the printing governs the verse flag, not the metre. 模 is mó at 身模 — the sense 康熙 glosses as 形, shape — and 觀 is guān, 分 fēn.
Eight Rules waits until the fight has reached what the text calls its sweetest point and then attacks from behind. Nothing in the passage suggests this is thought dishonourable; the only reason it fails is technical, which is that the creature he is stabbing has eyes on the back of its head. The narrator supplies that fact only after the blow has been struck, with 原來 — as it turned out.
What follows is a small piece of exact choreography. One shafted weapon, used at both ends: the ferrule on the butt fends off the rake behind, the blade on the head holds off the cudgel in front. It buys him five bouts or seven and then fails, and the failure is what forces the transformation.
The passage ends on the couplet that is not marked as verse. Seven graphs to a line, perfectly regular, printed on a prose line and therefore authored as prose — the source's indentation decides this, not the metre. It also does the work a verse tag would do, announcing that a description is coming and telling the reader in advance to be frightened by it.