Overlords+ get a ability called Drill. Basically it allows them to drill up to a 10x10 tunnel. With each 3 stone mined it costs them one dirt. It mines ores but just gets rid of them. A Ore drill. This is the same as a drill, but 1 stone each time 1 stone is mined, and it doesnt mine ores, so there are ores floating around.
Wizards+ get a Jetpack, which allows them to fly around, it isnt powerful, it can take you up 1 block per second but doesnt have fuel
Masters+ get a Torch, this is like a lantern, no XP boost but it works like a real torch, so it shines where you point it. Good for caves
With each level up, a speed boost would be good, because it can take FOREVER to get around.