Of all the alien civilizations that humankind has encountered in our travels through the Milky Way, none has begun to approach the power and influence of those called the Lattice Builders. The construction of a planet defies all known economic and logistic skills -- and the Lattice Builders have built not just a single planet, but seemingly an infinite number of them. Spread in a two-dimensional grid that extends without apparent limit, and spaced at distances of over five light-years, the Lattice Worlds stand as a tribute to the unimaginable power of a species that has, as far as anyone knows, chosen to leave their creations unattended and subject to occupation by whoever might find and claim them. Humanity has claimed a large number of Lattice Worlds, and so have many other alien species, undeterred by the possibility of the Lattice Builders' return.

Each Lattice World is a self-contained habitat, with heat and light sources, an inexhaustible power supply, and machinery to create whatever materials or objects that the planet's occupants might need (but if only those occupants can master that machinery!). Many of the Lattice Worlds are "blanks" -- unfeatured, smooth, dark balls of iron ... but a small percentage of them possess sculpted terrain and atmospheres of various shape and composition.