Spider guard is a more advanced guard application, but very useful for controlling and setting up submissions from.
This video is from Caio Terra covering some spider guard concepts.
This next clip is from Ricardo Cavalcanti, demonstrating how to get from guard to spider guard and some attacks from it, followed by how to pass the spider guard.
Draculino teaches an omaplata application from spider guard.
Leo Veira teaching how to pass spider guard.
Kurt Osiander teaches a spider guard counter.