The Boss family is a family that is exclusive to the Monster series.
Monsters in this family are typically evil lords that serve as the major and final bosses in the mainstream games. The Incarnus from Dragon Quest Monsters: Joker 1, 2 and 3 is also in this family. The monsters in this family are some of the most difficult to synthesize in the series, no different than Rank X monsters in the other families. With a few exceptions, monsters in the boss family cannot be recruited and must be bred/synthesized to obtain.
Monsters in the Boss family serve as the bosses at the end of the post-game family gates. These monsters must be bred in order to obtain, and every one of them require the most complex recipes. It should be noted that nearly all members of the boss family are required to obtain Darkdrium, the most powerful and difficult-to-obtain monster.
Once again, monsters in the Boss family are some of the most difficult to breed for. This time, the |ultimate |forms |of |certain Boss monsters (not seen in the mainstream games) are obtainable. The only Boss monster that is not obtainable via breeding is Darck, the final boss of the game. Instead, his egg is available post-game from the TinyMedal man, in exchange for 10 Mini Medals.
A feature unique to this game is that Boss monsters can be found in the wild (within the Magic Key worlds, indicated by the "Lord" prefix). None of them are recruitable, however, so the breeding requirement does not change.
The Incarnus is introduced in this game, and its line is the only monster species that are included in the Boss family. The other monsters that would normally be in the Boss family are instead categorized as Rank X (or Rank S, in a few cases) monsters in other families.
As a change from the previous Joker game, some of the Demon Lord monsters are reinstated into the Boss family. The Incarnus remains in the Boss family. Leonyx and Rigor Mortex are included in the Boss family as well.