Survivor Driven Mob

If Survivor Driven Mob would die, put a -1/-1
counter on it instead.
When Survivor Driven Mob has four -1/-1
counters, it gains "Remove a -1-1 counter from
Survivor Driven Mob {2}{b},{t}: Gain control
of target Zombie." until it has no counters on it.
While Survivor Driven Mob has four -1/-1
counters, its type changes to Human and color
changes to White.