Hexblade, Dark Companion & Knowledge check

[Shin Okada]

Do you allow PCs (and NPCs) to make knowledge check for recognizing Hesblade's Dark Companion (PHB2) to be not a real creature but an effect created by the class feature?

I guess Knowledge (Arcana) should work but am not sure how much DC should be appropriate.

 

[Dandu]

The PHB2 gives knowledge checks for identifying a Hexblade. You could probably adapt those for recognizing a Hexblade's class feature.