Chain Lightning

You create a bolt of lightning that arcs toward 1
target. 3 bolts then leap from that target to as
many as 3 other targets, each of which must be
within 30 ft of the first target.
A target makes a Dex save and takes 10d8
lightning damage on a failure, or half as much
on a success.
At Higher Levels. Each extra spell slot creatures
an additional bolt after the first one.