Kylo Ren’s crossguard lightsaber is an ancient design that recalls
weapons seen millennia ago during the Great Scourge of Malachor. The
crossguard blades, or quillons, emerge from focusing crystal activators
that split the lightsaber’s plasma stream into three channels, with the
quillons appearing after the main blade ignites. The crossguard blades
allow Ren’s saber to operate safely – his weapon is constructed around a
dangerously flawed kyber crystal, which would be overloaded if not for
the lateral plasma vents that create the quillons.