Overseer of the Damned board wipe
Assuming your opponent had two copies of Grizzly Bear it would result in all three creatures being destroyed and afterwards you placing two 2/2 Black Zombie creature tokens into play tapped.

Overseer of the Damned has a triggered ability which is placed onto the stack the next time a player would get priority. Put more succinctly, the ability doesn't go onto the stack until after the board wipe has finished resolving.