Automated defenses were no match for the Furling. They breached the iris without mercy.
Chickens
I know long standing fans will roll their eyes, but I've always objected to the idea that because of the name we've seen the images commonly projected. They lived on a planet they called Furl. Like our Earth. Has nothing to do with their appearance.
I think they were probably reptilian-like myself. Based on absolutely nothing, because there is nothing. Damn Asgards went to the grave not telling anyone, and the Ancients are so stuck up they never say anything. I'm okay with the Nox not telling us, they're good people and would tell us if it became important.