Celestia drifted in and out of consciousness as the valve controlling her blood flow was periodically opened and closed. She was dimly aware of activity around her, of excited voices, of shouting in a language she didn't recognize. It was hard to tell how much time had passed. An hour? A day? A week? No, her spell would have worn off by then.
Would any pony even be able to find her?
Every now and then they poured a mixture of water and grain down her throat and she did her best to swallow properly, but her weakness proved too much and she inevitably wound up coughing some of it up as they poured too quick. Then they would get angry and she'd feel the life leaving her once again.
This all repeated a few times before Celestia realized that she was slowly gaining strength. Each time they came to open the valve again, she felt a little stronger than last time.
They must be underestimating how much blood to draw, and she was healing more of it than they were letting out. And despite the shaft now pressing painfully hard into her horn struggling to heal around it, she found herself regaining some limited control of her magic. Not nearly enough to escape--she would at least need to teleport for that--but maybe enough for some tricks. If only she still had the power of the Sun on her side!
The first moment she could risk it, she cast a simple illusion spell that would make her seem worse than she was, hoping they would not notice her gaining strength. It was several more shifts before she dared casting any more magic, but finally, she had an opportunity.
She focused for several seconds first, building as much power as she could muster into her frail and pain-struck horn, before finally letting it go in a silent pulse, a ripple across the ether.
The effort drained her and she felt her consciousness slipping away again, but she hoped Twilight Sparkle was close enough to feel her cry for help.