List of monsters by Rarity:
There are many different rarities in Monster Legends,
The best ones are Legends. Then there are Epics. Then Rare, Uncommon and lastly Common.
There is a new Legends nearly every special event.
Legends are some of the best ones you can get.
Some monsters are unbreedable and can only be found in special events.
Legend - Has the element legendary in it, evolves to adult at level 25.
Epic - Evolves to adult at level 20
Rare - Evolves to adult at level 15
Uncommon - Evolves to adult at level 10
Common - Evolves to adult at level 7, has 1 element.
If anyone finds out how to breed any monster—especially Legends— please mention in the comments.