From publisher blurb:
The treasure of the dungeon calls to all who wish for riches, not just the player characters. In their adventures, it is likely that the party will encounter others who seek fame, glory, and gold, and those fellow adventurers are sometimes already in the dungeon complex that the group has decided to explore today. In such instances, the twelve adventurers described on these pages will help the GM when it comes to describing the opposing adventurers.
As with other works in this series, the characters detailed in these pages are without game statistics. I have offered up character descriptions and suggestions for power level and carried gear, but you will not find detailed game stats for any of the rival adventurers. And to be fair, you often need no more than is included if the party enters into a roleplaying encounter with these characters.
If the meeting results in combat, one very easy way to stat these characters is to make them a near-exact duplicate of one of the player characters. By using the same stats as the characters that are operated by the players, you simplify your workload and can be sure that the opposition is fairly evenly matched to the strength of the heroes.