Hmmm. I'm a unique case among Heroic Spirits, so all we need to do is link us. It's a verbal contract at heart, anyway.

[considers . . . then smirks] Give me strength, and I will protect you should you require it, should I choose to do so. I, Gilgamesh, King of Heroes, will be your sword, should I see fit. Tell me, are you the one who commands me?