Quote from Stapler »Ral, Storm Conduit's -2 ability is the link you are missing, I believe. Use the -2, then cast Doublecast, causing Ral's delayed trigger from the -2 to trigger, copying Doublecast. Let just that copy resolve, then cast any Fork variant targeting the original Doublecast still on the stack. The delayed trigger from the copied and resolved Doublecast will trigger, doubling your Fork, which you use to copy the Fork still on the stack, resulting in infinite copies and Ral triggers.
That does work! Thanks for explaining it. So both Howl of the Horde & Doublecast plus any Fork get the job done, or any combination of a spell plus two Forks.