Simple, right? Rainbowmon are given to players on a regular basis, ranging from low-star drops to high-star ones from events. Normally you have to level up monsters before evolving them. Rainbowmon will usually come at MAX level, cutting out that process entirely. Some things to keep in mind:
Rainbowmon save time, but you don’t want to farm for them specifically. Don’t waste other fodder leveling them up. If they come at MAX level, evolve them once and then stop. Afterwards, use them to evolve fodder you’ve gotten to MAX level. Making a 6* costs 100-120 3*. Rainbowmon reduce the time and resource cost.
Where Do You Get Rainbowmon?
Rainbowmon have a chance to drop from pretty much every relevant stage in the game. This includes Dungeon stages like Giants and Dragons, elemental halls, Rift, and so on. They also have a slight (~2%) chance to drop from Faimon Hell 1, which is the premier EXP farming stage. This means that you shouldn’t farm for them specifically. Instead, you’ll gather them over time while farming other necessary resources. They’re also given out during in-game events here. For example, the current 8-year anniversary event offers both 4* and 5* Rainbowmon.
Evolving Rainbowmon
You can see that the Rainbowmon from the Hall of Magic are already MAX level. Dropped Rainbowmon will always be MAX level. This is not the case for event rewards. This makes them easy to evolve. Instead of spending time leveling them up, you can evolve them right away. Rainbowmon can’t be taken into battle, so after evolving them you can only level them up by feeding them other units. Don’t do that, though.
Or Use Them as Evolution Material
After evolving them once, it’s better to use them as evolution material for other fodder. In my case, I’m going to use them to evolve a Wind Inugami that I leveled to MAX level 4*. If I didn’t have the Rainbowmon, I’d have to level up 16 different 3* units, so having them saves a lot of time and energy. 5* Rainbowmon will save you even more time, since you can use them to evolve an existing 5* to a 6*. In this case, I was given three 5* Rainbowmon. Each one is equivalent to 20 MAX level 3* units that I would have to otherwise level up. So using these Rainbowmon means I’ve saved sixty 3* units, and a lot of time. Note: Rainbowmon will save you a lot of time and energy, but you’ll still have to level up fodder the old-fashioned way. Enjoy your time in Faimon.