Uranus and its six largest moons compared at their proper relative sizes and relative positions. From left to right: Puck, Miranda, Ariel, Umbriel, Titania, and Oberon
Puck is an inner moon of Uranus. It was discovered in December 1985 by the Voyager 2 spacecraft. The name Puck comes from Celtic mythology and English folklore.The orbit of Puck lies between the rings of Uranus and the first of Uranus' large moons, Miranda. Puck is approximately spherical in shape and has diameter of about 162 km. It has a dark, heavily cratered surface, which shows spectral signs of water ice. The moon Puck would be very hard to terraform. It has a diameter smaller than Mimas, and most likely has gravity as low or lower. The terraforming process would be similar to Proteus.
Because of the signs of water ice, one rather interesting(and difficult) theory is that terraforming Puck would involve creating a largely water-based biome. Puck is small enough that you wouldn't encounter any areas with high PSi(water pressure), but whether or not this is actually feasible is up for debate.
It is, however, abundant in minerals and it's been suggested that it would be a good candidate for early off-world mining.