My first creation using the new execute command (The dynamic light command tutorial doesn't count). The power to absorb the soul of mobs, who don't want to have that kind of power? All living mobs around you will suffer from wither effect, and when they die, their soul will be yours. You can actually add more effects rather than just regeneration effect, all you have to do is copy the command used in the regeneration effect and put the command at the top of it, make sure that you don't put it before the command that kills the soul when it reaches the Soul Absorber.
The command was tested in 1.19.11