Depends on the details of who's giving the power and how, at my guess. So far I haven't been treating Might like something my characters are actually aware of or can manipulate; It's just a measure of effort and exhaustion. To 'give' Might would be to put effort into something and then pass that on.

Which could still obviously work as a general buff, permanently or for a limited time, but it could happen in a few ways. A temporary blessing from Niciel might be access to spectral wings and the ability to make things using Holy Magic for a few days. Zephyrion could give a mortal a few moments worth of control over some elemental swarm, while Jvan could give unlimited shapeshifting.

Bonus points for including an actual mechanism behind the time limit- A single bottle worth of potion, a scarf that wears out (or unravels), a fiery sword that slowly burns to a useless stump.

Capy did this really well when Ilunabar gave Meimu the Ring of Blooming- It would be easy to say 'let there be flowers', but instead we had a few moments of a powerful artefact on display that can still act as a device for character development even now that it's depleted.

ed: Speaking of shapeshifters, why the hell didn't I think of that sooner? hn hn hnn.