For the tempting vices, which fight against us in invisible contest in behalf of the pride which reigns over them, some of them go first, like captains, others follow, after the manner of an army. For all faults do not occupy the heart with equal access. But while the greater and the few surprise a neglected mind, the smaller and the numberless pour themselves upon it in a whole body. For when pride, the queen of sins, has fully possessed a conquered heart, she surrenders it immediately to seven principal sins, as if to some of her generals, to lay it waste. And an army in truth follows these generals, because, doubtless, there spring up from them importunate hosts of sins. Which we set forth the better, if we specially bring forward in enumeration, as we are able, the leaders themselves and their army. For pride is the root of all evil, of which it is said, as Scripture bears witness; Pride is the beginning of all sin. [Ecclus. 10, 1] But seven principal vices, as its first progeny, spring doubtless from this poisonous root, namely, vain glory, envy, anger, melancholy, avarice, gluttony, lust.
I notice, incidentally, that a lot of online sources get St. Gregory's list wrong, assuming that he, like later authors, folds vain glory into pride. But in Gregory's account, pride is a distinct vice; vainglory is a daughter vice of pride, and, indeed, all of the capital vices flow from pride as generals from a queen.