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[Ben 10]

And what are Midium?

[Mirandu]

Medium:
- Disguise
- Dullahan

Large:
- Gibbet

Small:
- Hylozoist
- Lude
- Quve

(by Rocards.de and Roempire.com)

Soo.. it seems people who kept saying, Dullahans were large monsters, are wrong.

But I think rocards.de and roempire.com are right. Why? Because the "Pierce"-Skill from a Knight hits a Dullahan TWICE (means -> Medium monster), and a Gibbet THRICE (-> Large monster)

[Ben 10]

Now, thats a good tipin xD, i understand now 
Thanks Mirandu