TEXT: 
  Looking for ways to trip up those pesky, over-powered
  characters that are stomping through your campaign? The
  traps detailed in this series focus on effects that target
  imbalanced groups.
  The fifth entry is called Magnetic Personality. This trap
  specifically targets creatures who wear metal armor. While
  strong characters may be able to avoid the deadly parts of the
  trap, a well-balanced party will excel against it.
  
  Simple trap (level 5-10, deadly threat)
  The characters enter a room with only one exit at the far end.
  On their left side is a large chamber in which the north wall is
  completely magnetized. Any creature wearing medium or
  heavy metal armor is pulled straight to it. And if that's not bad
  enough, they've got to pass through a beam of electricity as
  they go. Finally, the door at the far side is locked. You can give
  the lock any DC you like for breaking or picking it (suggested
  DC 15 or less).
  Trigger. This trap is constantly activated. At your discretion,
  you can offer a button somewhere else that turns it off.
  However, its default mode should be on.
  Effect. Any creature wearing metal armor or made of metal
  has its movement speed reduced by half by the magnet and it
  has disadvantage on all Strength and Dexterity ability checks
  and all attack rolls. Also, creatures wielding metal weapons
  make attack rolls at disadvantage.
  The first time a creature wearing a suit of heavy or medium
  metal armor enters the room or ends their turn in the room,
  they must make a DC 15 Strength saving throw against the
  magnetized wall. A character already restrained by the
  magnetic wall need not make the save until they free
  themselves. On a failed saving throw, the character is flung
  35 feet towards the magnetized wall, taking 3 (1d6)
  bludgeoning damage for every 10 feet they travel before they
  hit the wall; they are then restrained by the wall.
  A creature restrained by the wall can use their action on
  each of its turns to make another Strength saving throw,
  freeing itself on a success.
  The electric beam is an 80-foot-long line that is 5-feet wide.
  If a creature passes through the electric beam as it is pulled
  towards the magnetized wall, walks through the beam, or
  ends their turn within the beam, it automatically takes 7 (2d6)
  lightning damage.
  Countermeasures. A successful DC 15 Wisdom
  (Perception) check reveals the wiring that operates the wall. A
  successful DC 15 Intelligence allows a creature to disable the
  magnetized wall. Once disabled, all creatures made of or
  wearing metal are freed and suffer no further penalties.
  The electric beam's generators are easy to spot. They can be
  disabled with a successful DC 15 Intelligence check using
  proficiency in thieves' tools, or they can be attacked. Each
  generator has an AC of 13, 10 hp, and immunity to poison and
  psychic damage. Only one generator needs to be disarmed or
  destroyed to shut both down.
  
  There are numberous ways that this trap can be made more
  dangerous.
  Monsters in the Room. Because of the disadvantage that
  the wall applies to creatures wielding metal weapons, one
  nasty trick is to add in some monsters. The monsters don't
  even need to be tough. They can simply be annoying, sucking
  up valuable action economy from characters who are stuck to
  the magnetized wall or are trying to disable the lightning
  beam or the wall itself.
  Spikes on the Wall. The wall deals bludgeoning/falling
  damage when a character is flung into it, but if they're less
  than 10 feet away, they suffer no damage. Fix that by adding
  spikes to the wall that deal 3 (1d6) damage every time a
  character hits the wall.
  This is unofficial Fan Content permitted under the Fan Content Policy. Not approved/endorsed by Wizards. Portions of the materials used
  are property of Wizards of the Coast. ©Wizards of the Coast LLC.
  
SOURCE: textdata/thevault/Dungeons & Dragons [multi]/5th Edition (5e)/3rd Party/DmDave/DMDave - Magnetic Personality.pdf