The Rat is a single child of the De Puce family, who inherited lands and title after his parents lost at sea during their return from vacation. Due to his lack of education, he turned to his neighbour Duc Beauregard (the Snake), in order to learn economic and military leadership from his advisors.
In the beginning of Stronghold, the Rat's scouting parties encounter the Boy, who constructs a fortification in his homelands. Much to his failure, the Rat's scouts are eradicated and consequently he becomes worried of the escalating situation. The Snake advises de Puce to send a small siege force to cut the enemy's way of escape, however the force is defeated and he loses his first county in the counterattack.
As a reaction, the Rat blockades the county and offers truce in exchange of retreating Lord Woolsack's troops from the seized county. Soon it is revealed that the agreement is merely a trap and the advance party is slaughtered. Sir Longarm mobilizes and leads an all-out attack, taking away even more land from the Rat. This act not only tips the Snake off balance and leaves the Rat's forces in disarray, but it also incites a rebellion with the lead of Lord Manikin. Duc de Puce appears helpless, as the Snake leaves him and takes claim of his county as well. The Rat attempts an attack with enormous fources against the Boy, however the army is vanguished.
The series of failures grab the attention of Duc Volpe (the Wolf), who instructs the Pig to hand a large relief force under the command of the Rat. De Puce personally leads the army into a final attack in order to retake his castle, which was recently fallen to the rebel forces. During the siege, he is mortally wounded and he meets his demise.