Adding Population

[lyze]

I was thinking of a spell I wanted to try to make but I'm not sure if its feasible. I've searched the forums to see if anyone had previously posted something similar but couldn't find anything, however, I might not be searching for the right terms.

I am wondering if there is some sort of effect that can be applied to either a unit (whether troop or commander) or to a spell that can add to a provinces population. I know there are some units that have a 'kill population' effect and some spells kill population, does the opposite exist? If so, is it set number of increase, percentage or can it be either or?

Thanks for any help.