Language
Every species in the star cluster has its own common language to facilitate communication with other members of the same species. There is no equivalent for interspecies communication. The accessibility of technology removes the need for developing a common language, since translators—technological or otherwise—allow everyday interaction to occur without everyone having to learn a new language.
That being said, Terranglo is incredibly common as a second major language for non-Terrans, seeing as they have such an established foothold on trade in the star cluster. Traders, diplomats, and other interstellar lifestyles almost require someone to be multilingual.
Without a translator or a language you share in common with another person, you are unable to speak with them, and you’re unable to perform any abilities which require you and your target to understand each other. Magic is bound by the same rules as verbal communication—even if it allows you to communicate through telepathy. People are assumed to think in their known languages, so inter-lingual communication would be difficult even with telepathy. At best, you could convey vague imagery, though even this may be a barrier if the person you’re establishing telepathy with has aphantasia or a similar mode of thought.