Beasts - Tier 1: The standard beasts.
Low-class Danger Beasts (Tier 2): Stronger than typical beasts. An experienced soldier can handle them.
Mid-class Danger Beasts (Tier 3): Only elite soldiers can handle these.
High-class Danger Beasts (Tier 4): A shingu user can take them on.
Special-Class Danger Beasts: A teigu user can deal with these.
Tyrant-Class/Apex Beasts: These require someone like Budo or Esdeath to handle.
groups of people can take on beasts from a higher tier.