The mother-tree is the mature form of the starfly. It is a vital plant for space-faring elves, who have modified its seeds in a variety of ways.
When a starfly falls upon a comet, it sprouts roots into the rocky ground, digesting cometary ice and minerals. The sapling grows winglike leaves that absorb sunlight, and develops a bulb that stores water from the melted ice. The wings then become reflective, and focus sunlight on the bulb, heating the water and causing the steam jet to push the comet closer to the sun. Once close enough to the sun, the leaves fall away, leaving the comet in place.
In this phase, the mother-tree absorbs the remaining ice and minerals in the comet and continues to grow large. Once the comet's resources are depleted, a mother-tree has typically grown large enough to generate a gravity plane and hold an air envelope. The gravity plane continues to funnel rocks and debris into the plant's organic furnace, where it continues to absorb minerals. Once the tree has grown to about 1,000 feet, the smelting pods whither, and their decay produces air.
At this point, dense clusters of leaves begin to sprout, creating a habitat for living creatures, which provide the tree with the breath it needs to live. The gravity of the tree continues to pull in rocks, and, eventually, the tree forms the core of a new world.
Elves have reportedly been able to attach spelljamming helms to mother-trees, turning the entire tree into a great, living vessel. The elves are rumored to be using this as a basis for a new fleet, succeeding their amaradas.