A consequence of transfer with Ilyana when she was suffering Underdraw.
(Source: Unto Zeor, Forever, Ch 18) 'Like a stroke of lightning, her selyn raced into those secret, long-denied passages in himself, touching off a cascade that awakened simultaneously all the levels and depths of his secondary and primary systems. Suddenly all the intimate sensations possible only to a developed channel swept through Digen.'
Cascade is a term used in Channel's Destiny and To Kiss or To Kill, and thus developes meanings over centuries.