Alicorns are immensely long-lived creatures, with few others matching them. As such, their biology dictates they have heat cycles that are far less frequent, but far more intense, than any other pony. Celestia, after missing her cycle for a thousand years, is beginning to recognize the signs she will experience it. But no pony can help her sate it: she is sunlight incarnate, and will inadvertently destroy any who tries to please her during this time. She is far too dangerous for a pony to help, and the world will burn if she is not helped.

Yes, there is no pony who can help, but there is a certain friend of Twilight's who can...

Yes, this is a Spike/Celestia fic. And yes, they have hands: please note the anthro tag above.

Here's the link to the original (and amazing) coverart by ss2sonic, since it was removed due to NSFW-ness: just click right here.