Spike Balls are obstacles encountered in Hell. They consist of a pushable 'anchor' block, with an spinning spike ball that orbits around it at varying speed. Some are really fast and can stun-lock you by themselves while others seemingly don't move at all.
The motion of the ball is not impeded by otherwise-solid blocks and will pass over them in the foreground, and will never run out of momentum whilst attached to the anchor. The Spike Ball itself only affects crates, pots, the eggplant, snowballs, dead skeletons, lava buckets, monsters and the player. The anchor block acts exactly like the normal pushable blocks.
A great number of them appear surrounding the Golden Idols that spawn in Hell.
If the anchor is destroyed the Spike Ball will detach from the chain and smash through the level until it runs out of momentum, similar to a small boulder. The player should be cautious in levels with many Spike Balls,as it is very possible that letting a single Spike Ball free can also destroy the anchors to other Spike Balls. Anchor Blocks will also be destroyed if they reach the bottom of a lava pit and thus the release of their spike ball, which can be very surprising.
- The Weapon is likely a reference to the Ball 'n Chain in the Mario Bros games inside castles