Below is the text on the scroll Desmond is reading, it doesn't answer all questions regarding nether dragons so if anyone has any please ask them here.
Also big thanks to KiDra for helping me refine this text, it was very hard to write in a non-rambly way. If you're interested in more about nether dragons and venkats please follow A Story Never Told here, it goes into a lot about the importance of their relationship: https://www.sofurry.com/view/793750
My dearest Chani,
I have written this scroll as guide to questions you might be asked about nether dragons. Refer to it before you hold a bonding ceremony until you feel comfortable, and if you ever feel put on the spot, take a deep breath and ask Ailill for advice. Most importantly remember I am proud of you and the path you have chosen. You will make a fine Druid.
The Nether Dragons Nether dragons are faithful spirits that protect us in life and death. They preserve our memories from one life to another and keep our soul from harm in the Otherworld. They become a part of us, living in our bodies, sharing thoughts and emotions.
Venkats are born with a nether dragon or bind with one later in life. Those that are not born with them either are new souls or never bonded with one in a past life. Traditionally bonding takes place at the age of 14 during a what is called a 'Bonding Ceremony'. This is performed by a druid. Usually at the age of 14 a venkat's body is strong enough to support a nether dragon’s physical appearance. Having a nether dragon in the flesh allows a venkat to accept the new relationship more easily. It is not unheard of for a nether dragon and venkat to bond outside a proper ceremony, but it is uncommon. When a nether dragon is bound to a venkat it's physical body is supported by the host and can last as long as the Venkat lives. Their bodies can also be recreated if destroyed.
Nether dragons naturally exist in Otherworld and enter our own through conduits, primarily our holy trees. They are bound to this tree for only a short period of time, fading back to the Otherworld after a few hours. During this time they can create temporary bodies and interact with the world around them, but they have very little understanding of it and are instead driven by a strong sense of curiosity. Nether dragons who are bound to a venkat that is dead (their soul is in Otherworld) cannot enter the world through holy trees, but instead enter it when the soul is reincarnated.
A venkat born with a nether dragon will be aware of its presence on some level, but needs to learn to communicate with the nether dragon, much like learning to speak. Mostly they communicate with emotions and images, but once venkat and nether dragon are skilled enough, they can talk.
While a nether dragon resides inside its host you do not hear their voice physically, but sense them more like foreign thoughts. Be aware, that when a venkat is troubled by strong emotions it becomes hard to impossible to distinguish the words of a nether dragon inside you from your own emotions and wishes. It is the most fragile form of communication.
A nether dragon's appearance and gender is generally a subconscious decision by the venkat, when their first body is created, but it is not necessarily the final appearance of the nether dragon. For example when their personality and understanding of the world develops they may associate with the opposite gender more and change. Nether dragons that are freshly bonded might show inappropriate behavior, not knowing about concepts like shame, privacy, property and their like. They learn quickly, though and never mean harm. After two weeks they should know enough to no longer make their host uncomfortable.
That is all you need to know for a start and I am sure you will have no trouble gaining more knowledge about them yourself.