One can gather several unicorns to power a runic matrix. Option two, find a pony with enough magic to do it themselves. And finally get a crystal and enchant it to hold a magic reserve and use it as a buffer to power the spell. Out of all the options available to me the last one is the best as getting several ponies together or getting a pony with enough power would cost a lot and that's even if you can find anypony willing.