Uib

Deep Ones - Their actions at times are so alien and inexplicable that some speculate that their minds exist on a different plane of existence than their bodies. It is only assumed that they have some means of communication with one another because they display levels of organization beyond most Ib. Both psychic and magical means of communication are futile.
Sarkons
Whistlers - Communicate via musical whistling, some of which employs tones imperceptible to most Ib. They lack a natural writing system, though Human and Whistler scholars did manage to create a mutual dance-based language to communicate, which was later transcribed into a written form. However, the Whistler native language functions in a manner so vastly different from standard Ib tongues that learning this written language is difficult and only linguistic scholars ever learn it. The Dance form of the mutual language is considered to be a better compromise and has been adopted by a significant portion of the Whistler population, though most members of other Ib races do not bother with learning it unless they plan on becoming intimate with Whistlers.
Due to their unique oral cavities, Whistlers can only consume liquids.
Slimen - Most lack the ability to produce any vocalizations whatsoever and many lack a sense of hearing. They communicate through rhythmic vibrations, which in their poetry is perceived by most Ib as dance. Nearly every Ib lacks the means to interpret or produce these vibrations. While they can learn Ib writing systems, many of them lack the means of producing writing of their own, inhibiting the learning process and giving many of them less motivation to study as there is little appeal to learning what would be a one-directional language. This one-directional barrier can be somewhat surpassed through the use of Morse code, but communicating more than the most basic of messages through Morse is inefficient and as most Ib do not know Morse, only gifted and motivated Slimen tend to study it.
Yurei (Space Ghosts) - Enter a creature through a facial orifice and proceed to take over their body while consuming their soul, gaining very rudimentary knowledge of their victims skills and bodily functions in the process. They tend to prefer Ib victims because their higher mental processes tend to allow for more intense sensations. The victim loses complete control over their body over the course of an hour, after which time they still have conscious awareness of everything that is happening to their body and experience excruciating pain as their spirit is slowly drained to nothingness. After one day their soul is completely consumed and cannot be recovered. Yurei come from the dark places between the stars and have lives void of physical sensation when not possessing another creature. As such, when they do snatch a body of their own, they often ruin it through forcing it through the extremes of pain and pleasure and drinking in the intense sensations. When the body they are inhabiting perishes, they can simply possess another one. They cannot reproduce on Aum, but the bodies they possess can. Some of the more patient and sinister ones will bear children to subject them to all manner of horrors before possessing them. Yurei can communicate with one another through making physical contact with one another when not possessing a body, or through fluid exchange while they are. They can learn to speak Ib languages if they possess a capable body and the discipline to study, though such diligent yurei are rare.