The metal rod is typically iron with knobby bumps or sometimes short spikes. The wooden handle is often oak and wrapped or bound with leather and studded with tacks. The rod is attached to the handle by a "rope" of force about four inches long, not visible to sight not aided with magic.
The "rope" of force moves like a normal rope does, but since it isn’t an actual rope, it cannot be burnt, cut, soaked, or so on. Since it is a force, however, it can stop objects, so it can be used to parry, tie, or trip something.
The flail can be used as a normal flail, with no bonuses to strike or damage. Unless it’s full magic is activated, it simply has an unbreakable tether.
To activate the floating flail’s full magic, the weilder needs to imbue it with some of their life force (2 hp or so). If the weilder concetrates for a round (about a minute), they can change the length of the tether. It can grow up to 12 feet long (4 meters) and can move up to 200 pounds of weight.
If too much weigh is applied to the tether, it does not change in length rather than breaking or exploding. Each action of growing or shrinking takes a full turn. The tether can be shrunk to the point of being joined to the handle for all intents and purposes and then being wielded as a club.