Lighting rod mob grinder in 1.17.

Items needed:
Trident with channelling
1 Lightning rod
4 Pistons
4 Observers
1 Lever
8+ Blocks

The trident sometimes falls off the lightning rod so you have to replace it if it does.

This design is the old trident grinder with a lightning rod in the middle, I could not find who made the original grinder if you know who did leave a comment and I will give credit.