Magnetic Floor (5e Trap)
From D&D Wiki
This trap can either be triggered manually by flipping a switch located on one side of the trap area, or it can be set to be triggered automatically when 10 or more pounds of metal are in it. This trap can be spotted on a successful DC 15 Wisdom(Perception) check. The floor appears slightly shinier and smoother than the surrounding material. Any creature standing in the trap’s area of effect whilst it is activated and holding an metal weapon or wearing metal armor must roll a strength saving throw. The DC of the saving throw and its effects are dependent on the metalsource being carried.
Armor: DC 20; on a failure, the target is prone and restrained Weapons: DC 15 for weapons with the heavy property, DC 10 for weapons lacking the heavy or light properties, and DC 5 for weapons with the light property or small, miscellaneous metalitems; the weapon is stuck to the floor
At the beginning of each of its turns, a non-prone creature must make all appropriate saves. As an action, a prone creature may attempt to end one of these effects by attempting a Strength(Athletics) check with the same DC as the appropriate saving throw
If set to be triggered automatically, the trap deactivates when less than 10 pounds of metal remain in its area of effect.
Note: shields are treated as weapons lacking the heavy or light properties for the purposes of Strength(Athletics) checks and Strength saving throws; they can be treated as weapons with the heavy property or weapons with the light property at the DM’s discretion