From Gamesverse Wiki
Bound Familiars are almost a halfway point between Summons and Familiars - indeed they are called Bound Summons just as often, though they cannot be called from nowhere in the same way as True Summons. Certain non-sapient animals exist with their own Linker Cores, or analogous structures - an example being the worms from A's. They exist primarily on Type-3 worlds, but a few have been found on others - some spread through human action, a rare few having evolved there. While the procedure is much rarer now, mostly confined to a few tribes that have survived since those times and who still remember it, Alhazredians commonly bound such creatures to them, allowing the mage to tap the creature's Linker Core for power and direct it via the behavioural modification templates that were part of the binding. This is one of the sources for the prodigious magical strength that Alhazredian mages were reputed to have. Priest-kings in particular had not just one Bound Summon, but dozens - sometimes hundreds. Friedrich is an excellent example of what this type of summon is like - not something you dismiss, but a real creature that is merely empowered and made more intelligent, though rarely fully sapient, by the binding. And which has its own magical abilities, powered from its own Linker Core, which are potent in their own way - and will become more so as it learns and grows.