Well the Sphere has no idea who your (Silux) race is. Their slow and steady expansion followed by spamming FTL jammers everywhere over the course of 1000 years and ignoring everyone else has only recently been coming to an end with its involvement with foreign wars, Manchurian-Agent program and random appearances of Borg-cube style warships.

Actually, the Sphere doesn't really know about anyone beyond its immediate neighbors. It only just met the Graal (Which is pretty near by) 50 years ago... When it invaded it as retaliation for its invasion of human space.