Morgrim's Traps and encounters - Part 2 #

From the Dread Lord Morgrim's tome of Phylactery Defence comes advice for devious traps for any prospective Lich, Demon or Dungeon Master. Perhaps these inspire deadlier traps still.

The Polymorphing rug mimic #

In front of a large door, you should place a great big rug. At first glance, this is unsuspecting. Perhaps people will think there is a pressure plate hidden underneath but no, it's plain floor. Perhaps they'll test if it's a mimic and again no, it's just a rug. That is, until they go to kick open the door.

On the door is a Glyph of Warding with a spell prepared to cast polymorph on the rug. What is it being polymorphed into? A mimic of course! Once they kick open the door, describe what comes out as mist that seems to be grabbing at their feet if they should have anything like a sword of warning or anything of that nature that might prevent the mimic from getting a turn. As mimics are adhesive, the players are automatically grappled without any save or check for it which will astonish them and hurt them from the view of action economy. I would also adapt the Mimic statblock to have two changes, firstly acid blood so that anything that might stab at it will send acid spurting out everywhere and potentially corroding armour and weapons at grappled players who will struggle to avoid it(of course this should only apply to piercing attacks. Anything that is blunt doesn't do this). I would also adapt the Mimic's attack to be a special form of multiattack that hits all grappled enemies. They should also have advantage on their attack either from the unseen attacker bonus, or from its victims being grappled.

Even though the Mimic is a low CR rating monster of CR 2, I believe these changes to its statblock make it formidable and quite damaging to player resources if they aren't checking carefully for traps. As usual for mimics, if they go below 1/3 of their health(which is already a relatively small health pool and low AC), they should attempt to flee(though this may be hard due to their low movement speed).

The Leprechauns and Mirror Tunnel #

In this trap, there is a plain corridor leading to a chest. The length of this corridor should be suitably short to give players a feeling of some security that they can get out and hide, but long enough that all players could reasonably hide in it. Any successful attempt to investigate for traps should reveal grooves and subtle rotational movement of the tiles beneath them, maybe even slight grooves with the walls. Once the chest is opened, a mechanical trap triggers through a series of gear mechanisms that rotate all the tiles of this corridor and their associated walls and ceilings 90 degrees. This then pits each person on a tile against what appears to be two leprechauns.

One of these is a mirror that will visually copy the other leprechaun. This mirror is attached on one side to all the rotating tiles so if a player attacks it and cracks the mirror all players can see it is cracked. If you want a bit of flavourful superstition, you could even give the person who cracks it 30 minutes to an hour of bad luck, so they have disadvantage on all rolls.

The Leprechaun is a pretty pathetic creature who dies in a single attack. Their actions are Loot: with +10 to hit, and on a success, stealing half the players Gold Pieces, and a tuning fork with the spell planeshift prepared to cast(either by some kind of glyph of warding or by calling them sorcerers with metamagic to make it fit in the cast time, however you like). The Leprechauns are never seen from again.

This particular trap both hurts adventurers where it counts... their wallet! And is particularly vicious if you are also using shopkeepers.

The Golden Boulder Amphitheatre #

This is a trap nicked from Grimtooth's book of traps. With little to no deviation. A golden boulder lays on top of a set of circular stairs. The floor is a delicately balanced lever that with the weight of about 25-50lbs triggers and moves the boulder down. I ran this as written except for the boulder rolling into a pond of water and sinking to the black depths below outside of it for reasons we'll get to soon. I will note that a rather smart adventurer considered using an immovable rod(yes the one that lets you put 8000lbs of weight on a position) in order to prevent the lever from going down.

Abeloths and the Black Lake #

The main attraction of the dungeon floor I ran most recently is a black lake with many black ponds scattered around. Within this lake is an Abeloth that bides its time. On the first time disturbing the water you get its attention. Each time the water is disturbed afterwards, the player with the lowest wisdom who is not currently enslaved by it, must make a wisdom saving throw to not be enslaved.

In addition there is a ferryman. The idea with the enslaved player(s), is they will eventually hijack the ferry and lead them away from their destination towards murky depths to try and push their friends overboard. This puts players in a very difficult sandwiched position, between trying to get ashore, being grabbed and multiattacked(attacked 3 times by tentacles that inflict a nasty disease with +10 to hit) by an Abeloth.

This fight was terrifying enough that it forced the players to pretty much bolt and run away from it. Add in the lair actions and it's especially terrifying. I did admittedly make 2 errors when running this, I forgot to use its opportunity attacks and its legendary actions... though perhaps this is fine...

Conclusion #

This concludes the second part of Morgrim's everlasting miserable defences of doom.

Send all complaints of failed traps to "1, Dungeon of almost certain Doom and Misery, City of Yendor, M1S-3RY".

Published on 2026/02/09