User blog comment:Hitsuji Mamoru/Servant Creation Room 2 : Guess of the Who/@comment-28209103-20170326041552/@comment-4802891-20170326081138

It was easy enough, indeed... it would have also been a massive facepalm-worthy answer for not getting it right earlier.

Trickster fooled me a bit because I associate trickery with mischief, Loki/Hermes-tier mischiefs. Why is his territory creation and item construction so low tho? Because he can give the concept of creating one's territory and creating objects to human beings but can't properly use these himself?

Now, for the harder one... I'm not sure if your earlier comment about his brother being the harder one was to take as a hint or an example, but it would only be half of the answer since he is a composite Servant.