“Why would I lie to you? Twilight said we could stick a big enough gem in her head that it could act as a magic reservoir as well as the spell focus, that it’d be necessary so the spell doesn’t run down quickly and she, er, ceases to be. She thinks we can get a month of life in there, though we’d be topping it off regularly anyway. Big enough reserves she can be awake twenty four hours every day without us worrying. No organic body to maintain, after all.”