[quote=@Unoedipal]
Keep in mind that if he's being summoned in his birdman form, people will be able to figure out his true name much easier. You can have him be summoned with a normal human appearance in return for debuffs though, like Chiron. 

Change PC's description to "The capacity to hide one's presence as a Servant. Cannot be detected by normal methods, but can be detected through skills, magecraft, mystic codes, bounded fields, etc. Efficacy decreases when preparations to attack are made."

Natural Monster's description isn't all there. 

Change the NP type to Anti-Army.
[/quote]

Fixed.

Done.

Done.

I know, but that's fine by me. Secrecy is overrated.