So I'm running my first pathfinder game, and I wanted to introduce a few magic items to the campaign. One I had in mind was a sword that changes shape/size based on the temperature like mercury, so in an average temperate climate it is a regular short-sword (or longsword) but in a cold climate the blade would take the shape of a dagger, while in a hot environment it takes the shape of a longsword (or bastard sword). Ive read up on the transformative special ability and greater transformative I just want to see if maybe there is another alternative or other abilities that could achieve that effect.