Mail Balloons are small-scale airships commonly used by Delvers of the Abyss to transport letters and light packages to the surface from inside the hole. They can carry a reasonable amount of weight. There are two main types:
- The Gas Balloons are fueled with a gas harvested from a certain type of seeds that float due to gas within them. The plants are parasitic and turn the bugs that eat them into hosts for their seed beds. They don't exhaust over time, so they will not stop floating no matter how long the distance. Furthermore, the seeds are sensitive to changes of the atmosphere and will not leave the Abyss. Therefore, they conveniently come to stop near the surface where Orth is, allowing the Gas Balloons to reach an easily accessible spot. This makes these balloons very convenient to transport messages from below, but they have a weakness. The seeds are often consumed by large birds and insects that are confused by its scent. Delvers often use a bird repellent to keep them away from it, but it doesn't always work. Currently, these are most commonly used regardless.
- Hot Air Balloons are an older type that isn't seen very often nowadays. By using fire to boost the balloon upwards, the ballon continuosly ascends. These work fairly well for short distances but the fire sometimes goes out midway, and other times it ends up floating in the sky beyond Orth, which make them less reliable. When bringing one with you the coal, or other heat sources, can be unwieldly. It has the advantage that it often goes unnoticed by the local fauna of the Abyss though.