Mob Immunity plugin

So I need a plugin that can toggle mob immunity for a specific group on my server but can be toggled off in certain world guard regions with a flag.
permissions: mobimmunity.nodamage - mobimmunity.toggle - mobimmunity.*
commands: /toggle immunity

basically when you are hit the group would take no damage.

Really would like it for this to be made as i havnt found any other plugins i like for it.