Mod requests (orders).

I'm afraid that such things can only be initially предусмотрены by the game mechanics. Otherwise, it's pointless to even try.
However, there's an option for single-player games – combat scripts. Try creating a spell whose activation triggers a script. And in the script, apply vampirism sequentially to each cell in a 3x3 area. I'm not sure if such scripts are possible, but it's worth a try! This will only work in single-player mode.