Save state on virtual table
With the warlock or to avoid mistakes, add a save state or allow to rollback thru previous damage could be very useful.
It could be done by saving a damage history by player and replay thru it, reversing the data.
Basically, it just needs to know the four values (hope, health, armour, energy) modifiers, and re-apply them in negative (so 12 in armour and 5 in health become -12 armour and -5 health).