The Silver Wolf Cruel Bus is an armored vehicle with a cannon, akin to Tanks, except that it is not a Tank and is of the Fast type. The Cruel Bus is the "cruel" amalgamation of a school bus, extra armor and a stolen cannon mounted on its roof, delivering destruction in the form of a solid cannonball. The vehicle is similar to a Gun Truck except that it carries more ammunition and is much bulkier. This unit is a low priority because of its low offense of only 24.
The stronger version of this unit is the Magic Cruel Bus, which you will begin to encounter at level 55.
This is the Silver Wolf's version of the Gun Truck