Monster traps are trivial to set and upgrade using the alter command '+'.
They can be disarmed like any other trap.  The power of traps increases with
player level and disarming skill.  Monsters may sometimes disarm traps, or
they may be destroyed when they activate.  Monsters that trigger traps may
temporarily become wary and less susceptible to further traps.  Only one
monster trap may exist on a level at any one time, so disarm an old trap to
use your trap gear elsewhere.  If your trap is buried in rubble, you will not
be able to reset it on that level.
     There are 10 types of monster trap: the basic trap, and 9 advanced traps.
Advanced traps are created by updgrading a basic trap using the alter command.
As your level increases, you gain access to more of the advanced traps.  Most
traps are unreliable versus flying and insubstantial monsters.  The traps are
as follows:

   Basic Monster Trap - This is the fastest to set, and does the most damage
      of any trap.
   Sturdy Trap - This trap is less likely to be destroyed after activation.
   Netted Trap - Consistently affects flying monsters but is unreliable
      against non-flying monsters.  (Requires level 6)
   Confusion Trap - Confuses monsters but does not damage them.  (Requires
      level 12)
   Poison Gas Trap - Releases a cloud of poison gas.  Covers a good area, but
      does the least damage of any damage dealing trap.  Though the gas can
      affect any monster, flyers and insubstantial monsters will rarely
      trigger it.  (Requires level 18)
   Spirit Trap - Consistently affects insubstantial monsters such as ghosts
      but never affects others.  (Requires level 24)
   Lightning Trap - Shoots a bolt of lightning at the target.  May stun,
      unless the target resists electricity.  Consistently triggered by flying
      and non-flying monsters.  (Requires level 30)
   Explosive Trap - Releases a burst of fire and shards.  Does damage over an
      area.  Though the explosion can affect any monster, flyers and
      insubstantial monsters will rarely trigger it. This trap is always
      destroyed when it detonates.  (Requires level 36)
   Portal Trap - Does not damage monsters, but teleports them away.
      (Requires level 42)
   Stasis Trap - Places a monsters in suspended animation, so they can take
      no actions and can not be moved or harmed.  Does no damage.
      Consistently triggered by all sorts of monsters.  This trap is always
      destroyed when activated.  (Requires level 48)