User blog comment:Skeith9/Heroic Spirits Speculation/@comment-175.143.156.204-20140628040923/@comment-175.143.156.204-20140628145640

Okay, here is My full idea,

Grey at least qualifies as an Assassin class servant. He's a wealthy noble so he'll at least have a Golden Rule personal skill.

The Horcrux like portrait noble phantasm makes Dorian Immortal.

If he is killed or has his artificial spiritual body destroyed in battle His spirit won't be absorbed in to the grail immediately. Instead it will be absorbed into the painting.

Once his master has enough mana, He/She can resummon Grey in to a new spiritual body and continue fighting on the fields. the only way to ensure victory is to Destroy the painting or Gery's Master. After all no Master no mana, no servant to resummons, In fact the painting itself will disappear from lack of Mana.

The reason why I keep calling it Horcrux is because I don't know any other way to describe a device or object, that stores one's soul in it. THANK YOU Mrs. J.K Rowling! Know that Harry Potter stories can help when needed.