Galaxydids are the sonic symbols by which the Sentinels communicate with each other. It is a more or less mortal way of exchanging information. Each symbol corresponds to one of the Sentinels and has its own pronunciation. Its meaning for each Sentinel is unknown. These symbols are not translated into any known languages. There is a suggestion that galaxydids are needed as a form to fill it with meaning and pass it on to another Guardian, so it is impossible to translate them.

For a long time no one knew about galaxydids, only some Sentinels saw these signs in the image, and only immortal races over time gathered all the sounds together and learned their meaning in the lives of other beings. Some Sentinels shared the meanings of their symbols themselves, while some symbols were described after they had affected the life of the creature who had chosen it (the symbol).

Each of the galaxydids is a powerful source of energy that affects the living being who has chosen this sign as its guiding star. It is like a sign and sound influences the personality and destiny, so before choosing galaxydid should think carefully and know yourself and your shortcomings, so that the symbol does not bring discord in life, and complement the missing parts of it.

By choosing a galaxydid, the creature binds itself temporarily or permanently (depending on the choice) to the Guardian, whose symbol is the chosen galaxydid. The choice is purely voluntary, or the parents' choice if the galaxydid is instructing the child.