I had a dream about these alien-type things and energy crystals and a protagonist that uses broken ones to turn into a thing.

Here we see the human, one of the alien-type-things, and then the human mutating.

One thing I might do is combine this with my timeline-shenanigans quest idea into one big mass of ...questy

though I might yet do a more normal thing of just "use the thing and power up and have powers whee".

The protagonist likes moths.