Fork chain lightning

I want a spell that you cast like fork lightning so like 6 target are hit but then i want those 6 bolts to be chain lightnings.

find all enemies in range, check which are in front of the caster, randomly pick 6, cast chain lightning on each of them with a dummy caster.

How exactly do dummy casters work i've never used them, if theres a tutorial please place a link.

by "dummy caster" he means physically go into the editor and create a unit that will have chain lightining and be your "dummy caster"