I was talking with people about monster mechanics. I've written a lot of monster mechanics in the last few years. Here's everything my players have encountered in the megadungeon so far. I'm leaving off anything that simply deals any extra damage, or is just an added grab, since I use those so often.
1. You can see squirming bulges under their skin. Every hit, tentacle demon babies spray out around them. This creates a swarm. The swarms can merge, if they do, their hit-points are simply merged.
2. 3/day DEPOSIT EGGS on a grabbed target — CON save DC 19 or eggs are forcibly implanted in your flesh, 8d6 dmg and Con save every day DC 19, after 2 failures the eggs hatch into disgusting tentacle demon babies (an additional 20d6 dmg as they hatch out of your flesh)
3. CHAMELEONIC: Disadvantage on attacks against Veck, as his colors shift and meld into the background.
4. COMBO: First attack: Regular
Second attack: Disengage up to 15’, attack everyone in a 15’ line
Third Attack: Attack everyone adjacent to him
Fourth attack: Disengage up to 15’, Knock back up to 15’
5. They are NOT HOSTILE at first, unless they feel they can get a strong advantage and win with few or no casualties. They are very cautious, but will feed the players false information and lead them into traps if possible.
6. stone Armor reduces all incoming weapon damage by 5
7. Laser: Scintillating purple and blue pulsing laser 300 feet long, seeks a target that the mecha has seen in the last ten minutes by the most direct path available (lines only), and targets it and everyone between it and the target
8. EVERY ONE-QUARTER HP:
Vents a radioactive cloud in a 20’ radius around it. This incendiary cloud lasts for 10 rounds, affects people who enter it or end their turn in it, and also automatically poisons people affected by it until the end of their next turn.
9. IF IT TAKES A CRITICAL HIT:
A chunk of its black armor is torn off, revealing a fleshy pulsing spot underneath. If hit (as a called shot), the mecha takes double damage.
10. If anyone enters room, utters spell causing rooms to tip 90 degrees.
11. Able to cast a MASS CURE WOUNDS as recharge 4/5/6.
12. if you’re hit you’re restrained (the ball and chains grant a +10)
13. MIMIC: if you try to open it, you’re stuck to it with a weird sticky previously invisible goo, it gets to attack with advantage, attacks against surprised creatures are automatic critical hits.
14. at will can cast REPULSION, this causes target creatures within 60’ to immediately move their entire movement speed away (no save).
15. Also 1/day can speak a disgusting word, target Con save 18 or is polymorphed into a disgusting lizard.
16. 1/day can breathe clouds of poison in a 20’ cube that CON DC 18 or 2d10 dmg per round and poisoned and movement reduced to 10.
17. Targets opponent and adjacent enemy, each hit deals 4d4 dmg and a stacked bleeding, dealing 1d4 bleeding damage at the start of each round, this lasts until a Medicine check DC 20 or a 3rd level or higher Cure Wounds.
18. 1/multiattack, as part of the attack, the arrow stick in a person and radiate their power, must be removed as an action to stop the effect:
ELECTRICITY (8d6 in 20’ radius when impact and at the end of players’ turn, others may Dex save 18 to take half dmg, but if you’re wearing metal armor you’re at disadvantage)
19. STATIC (all words come out as hissing static in 20’ radius, spells with V impossible)
20. HOLD PERSON (whole body goes numb and is paralysed, Wis DC 18 to resist)
21. MIND CONTROL (DC 18 wisdom check, comes under direct control of boss as long as arrow is in him, acts at the end of boss’ turn, all attacks gain a +10 dmg)
22. BLINK (roll d20 at start of each turn, on 11+ target blinks into astral plane, swirling psychedelic fogs, monsters can be dimly seen as shadows, only vulnerable to FORCE and PSYCHIC effects, and end of turn target returns to material plane)
23. when someone walks under it, it falls down. +10 and advantage against everyone under it, for 8d8 dmg.
24. Cone 15’ roiling black gas that lingers until the end of the frog’s next turn: CHA DC 13 or reduced to 0 hit-points, and at the same time, maximum health halved, which remains permanent as a curse.
25. Bite +10 d10+10 and suck you for maximum health (gained as temporary hit-points)
26. Can forgo each bite attack to suck in—everyone gets drawn towards it 15’, first person who makes contact gets bit (Strength saving throw 18 to resist)
27. On death: 1. Sleep (no save) 2. Magic missile 5d4+5 3. Color spray 10’ radius (5th level) 4. Cause Fear on killer DC 15 5. Paralyse lower / upper body on killer Wisdom DC 15 6. Fireball 10d6 dmg
28. Snail slings: 1d4+10 dmg, and you’ve got a snail on you that traces corrosive and numbing venom on your body — d10 stacking dmg each round, and Con DC 15 or a random limb goes numb / paralysed. 1 R arm 2 L arm 3. head 4 torso 5 R leg 6 L leg
29. Immune to Weapons, Any weapon that hits it gets stuck in the slime baby.
30. They only attack bleeding people, they are fascinated with blood.
31. his hand leaves a mark, keeping you from healing, as a curse.
32. He’s blind! All attacks are at disadvantage, except his BITE attack is NOT if the target is GRABBED.
33. FOG: At the end of every other round, the fog inside them radiates outwards in a 10’ aura, dealing 1d10 poison dmg and adding a stack of poison.
34. When a spell is cast within 30’ of a blue jelly cube, it explodes, dousing everything within 15’ with blue slime (2d10 dmg).
35. attracted to characters with max HP
36. LICK for free each round +12 to TRANSMIT DISEASE (2d10 dmg to max health): 1. SPREADING WARTS 2. INSTANT RASH 3. CANT STOP SHIVERING 4. JUST REALLY TIRED AND THIRSTY 5. MASSIVE BRUISING 6. EVERYTHING HURTS A LOT
37. When it moves through the slime, slime sprays everywhere: everyone within 20’ of the SPIKED WAR MACHINE must Dex DC 15 or take 2d10 acid damage.
38. EMANATE BLACK SPERM at everyone outside 15’ from it (+12 for 1d12 damage, repeating at the end of each turn as the sperm burrows into you, it must be burned out with fire)
39. Movement 30, but he is a slime bender, when he comes to a slime pool it forms a bridge that ferries him across for free movement. He can climb up slime waterfalls this way.
40. 2 attacks per round with his halberd, +12 — 2d8+4 and a stack of poison — 1d10 damage per stack. Player takes 1d10 dmg per point of stack at the start of player turn. Poison is permanent until cured.
41. Expel Poison: Expels poison from his skin, everyone within 10’ must Con save DC 20 or take 1d4 stacks of poison
42. They only attack if someone comes through this room alone.
43. If killed, they explode in a mist of crystal, everyone within 10’ must Dex save DC 15 or be restrained by crystal that takes 20 points of dmg to destroy, or a DC 18 strength check.
44. It takes no damage from weapon attacks,
45. if you get next to it, it can attack by reaction +12 3d10 acid dmg.
46. When it moves, it SCREAMS. Wis save DC 15 or be Frightened and speed is reduced to 10.
47. His skin is SO THICK that he only takes damage if he takes more than 15 points — at that point he takes the entire load.
48. When they ask a question as an action, their targets legs cease to work until they are forced to answer truthfully, no save allowed (this is magic)
49. If they die, their comrades are able to resurrect them — they have trained this way to become unsurpassed warriors
50. aura 30’ deals Con save DC 18 4d10 poison damage every round (save for half), on a failed save you’re poisoned. Your skin gets hard and green.
51. Immune to all damage while wearing the ankh
52. Mass Polymorph (targets 1d4+1 people)
53. STRANGE BOW +12 1d10+10 and impaled into the wall, must take 2d6+10 damage to remove arrow and move
54. They’re so fast that when fighting in melee that almost never miss.'
55. Immune to time-affecting spells
56. Duration of all spells cast on them is reduced to one round due to time dilation
57. One holds a squirming squid creature which he wields as a weapon: deals 3d6+10 poison damage, leaves bright white stripes where its tentacles hit,
58. Other holds a bright red rooster which he wields as a flame-thrower; every round in a 60’ cube in front of him, can breathe fire for 8d6 damage (Dex 15 for half)
59. Resistant to magic,, if a spell misses or fails, it reflects off the shell directly back at the caster.
60. Speed 20, but it leaves a trail of slime, and if you walk through it you must make a Strength saving throw DC 18 or be stuck, and use your action to wrest yourself free, Strength check DC 18.
61. EXTENDABLE ROYAL GAUNTLET HANDS, like Hellboy’s gauntlet except it can shoot out
62. MASSIVE SERPENT BITE: A coiling hydra of serpents bursts from the ground, all in the 10’ area must Dex save DC 18 or 4d10 dmg, then serpents make three bite attacks +12 at 3 targets within 30 feet for an additional 6d10 dmg.
63. Dream Breath (5/6): 60’ cone, DC 18 Con or 18d6 Poison damage, and begin to fade from reality — For next round all damage dealt is halved, then save again; on failed save, unable to interact with objects or see more than 10’, then save; on third failed save, you are banished to the realm of dreams for one minute (everything overgrown, weird gravity, giant lamp-eyed cats watch you, it’s night time)
64. replace an attack to kiss a grabbed foe — +10 attack to cause to become glued to the triple-men, lose 4d10 max hp
65. Spells cast in his sight are randomly disrupted:
Roll d10
1. Target closest adjacent target
2. Target self
3. Instead of damage do healing
4. All targets also turn invisible
5. All targets also polymorphed into 1. cat 2. lizard. 3. dove 4. dog
6. All targets also fly d10 rounds
7. Spell slot not expended
8. Damage doubled
9. Targets disappear for d10 rounds
10. Spell disappears, comes into effect in d4 rounds
66. Ranged attacks automatically miss due to blowing winds
67. Attacks and powers against her take effect with a 1d4 round delay
68. One single bright green flower, it is poisonous, touching the flower causes you to take 1d10 damage every time you speak, one hour.
69. SLEEP WALL — Cast sleep in a 60’ long, 10’ high, 2” thick wall, any who passes through it must Wisdom save or fall asleep
70. Immune to the type of damage they last took
71. Advantage to attack hurt opponents
72. it fears cold. It flees from cold, though it will try to smother anything small, smaller than 10 feet cubed.
73. He is immune to weaponry and spells.
74. He is incredibly strong, he will always win a grapple, and after winning, will deal 8d10 damage per round as he methodically rips them apart.
75. He can break through locked doors and other barriers with an action.
76. ABSORB SOUND: All within 60’ have their SOUND ABSORBED: 3d12 damage and Con DC 19 or Silenced and Deafened for 1 minute
77. SCREAM All within 60’ must Con DC 17 or 4d10 damage and be deafened until end of next turn
78. WITHER: targets all foes within 30’, causing 12d8 damage, DC 19 con save for half, on fail also 1 levels of exhaustion and making it as if they had not eaten for a week, also causes them to lose a quarter of their bodyweight
79. DEVOUR: swallow a L or smaller target whole, provided they have 100 hitpoints or less. Attack roll, then swallows target, they take 10d10 damage immediately, then take 3d20 dmg per round.
80. They can scramble over the surface of the water They flicker and glitch when they move, they can pass freely through opponents.
81. The one wielding the dagger catches on fire, he deals 8d6 fire damage to anyone who starts his turn within 20’ of him, and anyone who moves into his aura. This heals his friends and heals him, it cannot be reduced.
82. If attacked it has HP 50 AC 15 and one attack, it spins and at start of next turn shoots a giant purple laser beam 10’ wide 200’ long Dex DC 18 or 18d10 necrotic damage, this destroys the limb knot.
83. Attack +12 4d10 and stick, thereafter dealing 25% total hit-points at the start of each round, and inflicting a level of exhaustion. After four rounds mosquito woman also receives two levels of exhaustion.
84. Its blood is poisonous, when a head is severed, poison blood pours out, if underwater all water in 20 feet is poisoned and deals Con save DC 19 10d6 poison damage, half damage on save, and poisoned (save at end of turn to resist), this poison lingers for 24 hours; over water, the poison sprays straight forward in a 30’ cone.
85. ANYONE FROM NOW ON WHO HEARS THE SONG: When he makes music, must make a Charisma save DC 20, on a failure he accidentally plays the Demon’s song instead, the effect does not work.
86. The song is louder and more clear here. When you hear it, make a Charisma save DC 20. On a failure, you feel sort of dizzy and out of it, you’re dissociating.
You now make Psychic saving throws with disadvantage, and psychic ability checks and saves are at disadvantage too. This lasts for 24 hours.
87. Mirror Images — Creates 1d4 mirror images, its impossible to tell which is which, they take no damage from area of effect attacks, and on his turn they each cast their own spell, dealing half damage, attacking illith varn causes the usual problems of mirror image, except each one must be dispelled separately as a 4th level spell, they are AC 19
88. Every time the wolfman takes damage, chunks of fur go flying, when they hit the ground they each turn into a wolf! It starts as a FIRST ITERATION SWARM. Every time the wolfman gains damage, if there is a swarm within 30’ feet and there is a way for his hair to hit the ground, the swarm gains 20 hitpoints. After gaining 100 hitpoints, it becomes SECOND ITERATION. After gaining another 50 hitpoints, it becomes FINAL ITERATION. At this point, damaging the wolfman creates another FIRST ITERATION.
89. When 2 or more targets move within 10’ radius of each other, shoot mini explosive grenades (DC 19 Dex or 4d10 damage)
90. BLINDNESS/DEADNESS. Afflict one opponent with blindness and deafness. No save is allowed, and the effect is permanent.
91. turn INVISIBLE at the end of each turn, this can be dispelled or prevented by the usual means
92. INCENSE BURNERS CAN CATCH SPELLS! A spell that is targeted within 20’ of the censer can be caught in the censer. As a reaction, make an opposed intelligence check (d20+10), if incense burner wins, it catches the SPELL, and may cast it as a bonus action next round
93.And as a bonus action cast a spell:
1. All allies in 10’ radius get +4d10 temporary hitpoints
2. All allies in 10’ radius get extra attack
3. All enemies in 30’ radius movement reduce to 0, cannot leave square (Cha save DC 18)
4. All enemies in 30’ radius damage halved (Cha save DC 18)
94. WARP MIND: DC 20 Charisma save and 2d12 psychic damage, and: 1. Fond memory permanently replaced with demon memory
95. They take out a big sharp drill and start drilling into your head. They only use this if you’re stunned, and it puts them at disadvantage to defenses.
96. Brain Worm (range 30, at will, DC 18 intelligence check or 6d6 psychic damage and take movement in a direction octopus guard desires, even into hazards and off ledges)
97. STAKES: If a vampire is incapacitated and then manually staked through the heart at melee, it will be paralysed but not slain. If conscious, it can be incapacitated by being grappled by at least two people. It can then be slain by beheading.
98. These vampires are jumpy: they can jump 30 feet as part of an attack (separate from their move), if the attack hits then they’re on you and can replace one of their unarmed attacks with a vampire bite.
99. Spell: They can do a dance which causes you to dance too, Wisdom DC 16 or restrained for one round, and 10d6 damage as your body twists and contorts
100. BLANK: Smudges an area in a 20’ radius for 1d6 minutes, no concentration required and can be canceled as a reaction. This area ceases to exist. Anything that moves into the area ceases to exist. When the spell ends everything in the area returns to existence. DC 19 DEX save to escape. Anything that touches it gets glitched into the blank. Portions of limbs and objects gets smudged, but you don’t take any damage if you touch it.
