Overgrowth Mandatory Reanimation Example

Uncontrollable unlife presents a little bit more of a design challenge than uncontrollable life. Yes, black plays with fire and takes risks with the player's own life, but lean too hard into that weakness in any one set and black can end up unplayable.

So I don't think I'm going to put mandatory graveyard reanimation in common. It's too powerful if there are no drawbacks, and when you put in drawbacks, it becomes too complex and difficult in common. Here's an uncommon zombie.

Clearly you don't want too many of these in your deck in a limited setting. I may have to adjust the damage it does to the controller downward, but I'd have to playtest.

The reason it reanimates during your upkeep is so that it can trigger reave abilities that turn. 

For common zombies or black creatures I'll do more simplistic things like force them to attack each turn or forbid blocking with them. I want to capture the feel that this is not the same kind of necromancy you see on other planes and the player is not in full control of this contagion any more than its in control of the mutations. And non-undead black creatures (like bats and rats) have access to mutate as well.