Monster breeding is the act of selecting two beasts to produce an ideal offspring. This system was first introduced in Dragon Quest Monsters, and continued forward into the sequel before being replaced with monster synthesis in Joker sub-series.
Pedigree & partner
The pedigree controls what family the newborn will belong to. For example, selecting a Hacksaurus as the pedigree dictates that the egg will hatch into a member of the dragon family.
All of the stats the infant will possess follow the same basic formula: (Sum of parents' stat)/4 + the "plus" value of the child. For example, if the strength stat of the pedigree is 300 and the partner's strength is 500, with the egg's Plus value being 1, then the egg's strength stat will be 201.
Because recruited monsters will hit their level caps long before 100, with a star mark serving as the indicator, it is important to consider raising this ceiling with each generation. The calculation for this is ("plus" value x 2) + the breed's natural limit.
For example, a Ewwnicorn+6 will have a new limit of 62, as that species stops leveling at 50.
The "plus" value (stylized as + in-game) is a general indicator of a monster's capability compared to it's parents. The value is determined by the sum of the parents' level at the time of conception, with the following intervals:
- Level 20~39: +1
- Level 40~59: +2
- Level 60~75: +3
- Level 76~99: +4
- Level 100: +5
In the event of two "plus" monsters being bred, only the pedigree's value is added. For example, a Dracky+10 bred with a Lips+8 and both monster's level sum is 100, then the egg will have a "plus" value of 15 instead of 23.
Careful breeding can improve a monster's innate elemental and status ailment resistances, superseding a breed's vulnerability if the "plus" value is high enough. For example, assume that both the pedigree and partner monsters have total immunity to Zap. In this case, if the resulting egg's breed is typically fully vulnerable to lightning but it's "plus" value is over +20, then the egg will instead have a weak resistance. If this same hypothetical monster's breed naturally had a weak resistance to Zap to begin with, and the "plus" value was over +40, then the added resistance would be bolstered to a strong resistance.
In short, a monster can be given a weak resistance to all attributes in the game if the player is patient enough and plans ahead before breeding. This system does not allow for turning strong resistance into full blown immunity though, preventing players from creating teams of "artificial" metal slimes.