You can modify your Beam spell to jump from target to target, hitting up to five enemies, at the cost of range - it is now limited to 16 blocks instead of 64. The jump range between targets is 4 blocks, but can be extended using Range modifiers.
The spell will never harm its caster. When the spell is used on a block, the chaining behavior does not occur, and it will act like a regular beam.
When jumping, the spell will try to prefer monsters of the same type. So for example, if you have a group of 4 zombies and 2 skeletons, and you target a zombie, you will always hit the 4 zombies and one of the skeletons.