Here is a demo of an enchantment im finished with on called chaining(i didn't finish it today but way before but was very busy so i couldn't share). It deals a maximum of 6.5 damage at level 3 and spreads to about ~6 mobs. The enchantment is also a bit smart and won't target pets, invulnerable mobs nor players in the same scoreboard team. It has a 85% chance to happen and has a small cooldown on it
There is also a unique interaction when you have a bad effect. And that is by sharing that bad effect with another entity(each entity has a 30% chance to get one of the effects. They can also get more than 1 of them at the same time). With a bit of probability math the formula is 25.5% * n where n are the entities.
If you have a lower damage sword, the effect will pick that weapon's damage instead of the default chain damage. There is sound but its lowered so turn your volume up to listen. Sorry for that