Transpores are the teleportation devices used to enter and exit the non infested underground portion of Lucien. They seem to be large mushrooms with a shimmering aura surrounding them. According to General Pil, they grow on trees, or at least don't not grow on trees... They can be found at stations in places such as the Lucien sewers or General Pil's parent's restaurant's basement, and one also appears to be in the catacombs under Cielis. Transpores can only be used for one teleport before they disappear.
At the end of Book 4, Emily uses a transpore go get out of the catacombs of Celis. During the beginning of Book 6, Trisha Spring identifies the decontamination room as a transpore chamber, suggesting that such transportation is not uncommon. Transpores are the primary method of entering and exiting the underground portion of Lucien. General Pil has a transpore leading to his parent's house, 500 miles north of Lucien.