Chapter 74: Bring Your Own Coffin
Cao Cao selects Yu Jin and Pang De to go relieve the siege of Fan; but there's some discontent about Pang De's loyalties, as he used to serve Ma Chao, who now works for Liu Bei. So Cao Cao is worried maybe Pang De's men won't be as committed to him as they need to be.
Thus, to prove his loyalty to the cause, Pang De buys himself a coffin and has it brought along with him, saying that it's either coming home with Guan Yu's head in it, or his own corpse. Pretty metal.
In the field, he has a couple duels with Guan Yu, but neither can overpower the other. Eventually, Pang De pretends to lose, then fires off an arrow which hits Guan Yu's arm. But any advantage that this might have bought isn't pressed because Yu Jin doesn't want Pang De to win more glory than him. This is the shit mentality that loses wars, people.
Guan Yu doesn't come out to fight any more for a while due to the injury, so the Wei forces pitch camp near the river. This ends up being bad news for them, because it's the rainy season, and a foresightful Guan Yu had dams set up a few seasons ago to hold the river back.
He orders the dams be broken, and Yu Jin's forces are almost entirely destroyed in the flooding; Yu Jin himself is captured. During the chaos, Pang De strikes down two of his own officers for suggesting surrender, and he starts hijacking Shu warboats to try and get back to Fan; but he's eventually knocked into the water and captured. Yu Jin is ultimately sent off as a prisoner, but Pang De demands to be executed instead, thereby proving his loyalty to Cao Cao.
The book doesn't say anything about the coffin he made such a big deal about, but I have to infer that it got washed away in the flood and nobody was ever dramatically put into it.