Aside from the original comic, another separate comic is currently being made.
Dream is a light being that takes the form of a skeleton, and guardian of the golden fruits holding positive emotions. He's the more playful and vibrant of the two guardians and also an altruist, but despite his exterior, he internally suffers as much as his brother. Dream has the mentality of a 10-12 year old child despite his physical age, as he was stuck in stone for most of his life, though he grows more mature as time passes.
He wore a blue shirt and a yellow belt with the initials "DS" on them, with a blue cloth with yellow stars tucked into the belt. He always wore a yellow cape with a sun on it he and Nightmare made when they were younger, which ended up getting torn up by the latter during a fight. In more recent years, Dream would be portrayed wearing a new outfit. (Seen here)
Nightmare is a light being that takes the form of a skeleton, and guardian of the purple fruits holding negative emotions. He is more closed-off than his other, brighter half because of the pain the villagers brought him when he was growing up, but fairly smart and cunning. After letting his emotions overcome him with help of the apples, he is corrupted by those negative feelings and becomes a nearly unbeatable creature of darkness, wishing to drown the multiverse in negativity.
Nightmare's weaknesses seem to be anything to do with light. Regular weapons are no use against him, as he just absorbs them into the black tar-like goop covering his body. Regardless, even light seems to be somewhat ineffective- he still appears nearly unbeatable. He is usually seen as a simple skeleton monster covered in a black tar-like substance with four large tentacles protruding from his back. They are made of the same substance. He is usually seen in fanart wearing what a classic sans would usually dress in, also covered in the black goop. He has one glowing cyan eye, the right socket seemingly having been covered up during his corruption.
A homeless cat-monster, having lost his arm and family in a fire. He becomes Dream's best friend after he shows him kindness, and sees him as the son he'd lost. He, later on, helps him while he was stuck in stone along with the guardian of magic by taking him away from Nightmare, though he ends up dying at some yet unknown point.
The guardian of the Tree of Feelings, and Dream and Nightmare's creator. Whilst stern when needed, she's shown to be calm and patient, though she looks down on all mortal life. She died protecting her respective tree from a human who was somehow strong enough to defeat her, thus leading to the creation of the two skeletons to replace her.
The guardian of the Tree of Magic, or Yggdrasil. Her personality is unknown so far. She is the one who vows to help break the spell that turned Dream to stone and becomes his teacher and trainer afterward. She holds a deep hatred toward Nightmare for everything he's done.
The guardian of the Tree of Life. As of now, nothing is known about him.