Monsters all come from a dimension known as "The Forest of Beginnings," and return there if defeated. Monsters come out of this dimension through glowing spheres known as "Gates". There are 23 different types of Gate in Rune Factory 4, varying in size and elemental alignment. Gates will continue to spawn monsters until destroyed.
To be able to tame monsters, the protagonist must build a monster barn.
Some species of monsters will produce items after being tamed. Said monsters will usually leave one of that item on the barn floor each day, including the day it is tamed. However, monsters that produce rarer items (such as Queen's Jaw or Dangerous Scissors) will provide their items less frequently. The level of the item produced is determined by FP, while the size of the item (in the case of of eggs, wool, and milk) is determined by the monster's level.
All monsters can help with farm chores (planting, watering, harvesting, etc.) when their FP is high enough, including item-producing monsters. Farm work, however, takes a toll on the monster's health. If a monster's HP drops below 50%, it will become fatigued (indicated by a black scribble in a speech bubble over its head). If its HP drop to 0, it will no longer be able to work (a skull and crossbones will appear in speech bubble over its head). The player can avoid this by rotating farm chores between monsters or healing the affected monster with food, medicine, or magic.
Taming and Stats:
To tame a monster, the player must give it a gift. A speech bubble with a heart will then appear over the monster's head. If the heart turns into a skull symbol, the attempt has failed and the player must try again. If the heart gets big and bursts, you got it. If the speech bubble does not appear at all, either the monster is untameable, you did not give it the right item (in the case of boss monsters), or your barns are full. Items with only negative effects such as Failed Dish or Weeds also cannot be used for taming.
Brushing monsters and/or attacking them using a weapon with a Love affinity will make them easier to tame. When you brush a monster, a speech bubble with a musical note appears. This speech bubble appears for every tamable monster, so if it doesn't, it means that that monster can't be tamed, or you weren't close enough to brush, or the speech bubble got off screen.
You can brush up to 15 times when the note bubble stops appearing, but brushing is not very recommended because the monster will try to attack you in the meantime. Brushing is more worthwhile if the taming item is too valuable and you want to save it.
The gift given to non-boss monsters can be anything (even colored grass and turnip seeds), but they prefer certain items specific to their species; usually the items they drop if defeated (ex, Silver Wolf and Wolf Fang). It is more difficult to tame a monster that is higher level than the player.
The higher the monster's level relative to your character, the less likely it is to tame. And supposedly the opposite is also valid.
Boss monsters will only accept an item specific to their species. For example, the Bane Dragon will only accept Rockfish Stew, while Thunderbolt will only accept Royal Carrots. They also tend to be more difficult to tame than non-boss monsters, so bringing a stack of their favorite item is recommended.
Training tamed monsters:
50% of the experience you gain while fighting will also be given to monsters in your barns. Monsters that are currently in your party receive the full amount of experience and level up faster.
Besides leveling, monster stats can be affected by several factors. Food dishes give a temporarily boost to a monster, exactly like for the main character. Daily brushing and gifts increase stats permanently for a small amount, and a monster's favorite item (taming item) results in a higher boost. Different items boost different stats.
Hidden status attack value: Items with special effects, such as poison or critical attack, build up a hidden value. For example, if a monster is given Rigid Horn, its Crit % is increased by 1%. Do this 100 times, and 100% of the monster's attacks will become critical. The same can be done with poison powder, lamp squid, etc, making it possible to make a monster that can apply several status effects at once with only one hit.
Battling specific enemies: Every defeated enemy raises one or more stats for the monsters on your side. For example, defeating magic-using enemies usually boosts intelligence and magic attack.
Riding monsters: Some monsters are too small for the player to ride, or are too awkward or dangerous to ride (like scorpions, or the monsters that are on fire) but most larger monsters can be ridden. Riding a monster offers several benefits (especially early-game), including unique attacks and increased movement speed.
Monster's location: While this page lists all monsters and the area in which they're found, some monsters only appear in one or two sections of a field or dungeon. If you're looking for a rare monster, the World Map lists what can be found in each room.