Iobel works almost continuously on her spell. By the time the wedding day rolls around, she actually has something that she thinks might work, but has yet to succeed in cramming the whole thing into her head for the one minimum instant necessary to have it to keep. It's big. Contingencies for different types of walls, affordances to allow the subject to breathe, failsafes to prevent falling through floors, guarantees of awareness of when it wears off - maybe she should prune some of these, maybe she can just hold her breath every time she goes through a wall, she's in a hurry -

She doesn't get her pruning done fast enough.