Skybound (commonly seen as [Skybound]) was a placeholder text used for titles when playing Granblue Fantasy in English.
Whenever a character, weapon, or summon is uncapped to a certain point, it gains a unique title in the Japanese version. These titles are not translated for the English version and instead uses "Skybound" as a placeholder for all titles.
Since June 10th, 2018Verification needed. , Skybound doesn't appear anymore in English version. Weapons and summons now have new official title for both English and Japanese version, while character's [Skybound] title is removed completely. Character's title is retained in Japanese version, though. It is unknown whether these titles will be properly translated by Cygames.