Like it says in the title. I am playing a pure sorcerer with the "skull" familiar. I don't know if this is true for other familiars but if I am possessing the skull through the radial menu, and near a hostile creatures/player the familiar will casts spells and interact with the hostile creatures as if it wasn't possessed. An example being, I could be running along the map past a hostile creature and the familiar will start casting negative energy protection (as it seems to in any default battle) stopping it in its tracks to perform the action. Not sure if this is fixable or just part of nwn:ee.
One odd bug with a possessed familiar is that even though I am hostile with its owner, the familiar is still friendly to me and cannot be turned hostile. This makes the familiar untargettable by any spells which only specifically affect a hostile target.