[Vastra blinks, a little surprised. Honestly she thought Loki might believe in himself, if he's suggesting he's a god.]

I am a Silurian. [If they're playing 'Show You Mine', Vastra figures she could at least play along.] From Earth, ironically enough. I am a little hardier than a mammal, technically speaking, but I do not live forever. Just a long time. [She gives Loki a little wry smile.]