An evolved form of slimes, Knights possess multiple armored cores. Their flesh is much more resistant to damage of all kinds and is capable of regenerating, they are also able to modify their flesh to resist specific forms of damage.
Mutability is also increased and allows a Slime Knight to combine abilities as well mimic more than the biological abilities of the beings they consume. As long as the ability is innate (either tied to the body or soul), you are able to mimic it. If the ability is much more powerful than you are, you will instead get a weakened version that is in-line with your current strength.
This mutability also encompasses the ability to absorb and digest solid or liquid non-organic materials like acid, gems, or metals. Your flesh then gains the ability to mimic the properties of those materials for defense or to harness any exotic abilities they may have.