Originally Posted by
Beni-Kujaku
More seriously, it's more something like an extension of an elder brain. There's always a bit of an elder brain at the center of a brain golem, and that elder brain can control and see through the golem as if it were here (in 2e edition lore, at least). After its purpose has been completed, the brain golem goes back and is absorbed back inside its progenitor. So it's both a calzone golem kept in the freezer for later, a flesh golem for brain-composed creature, and the poor man's Magic Jar.