d100 Dungeon Illusions and Phantasms

These are illusion type traps planted in dungeons by illusionists or other magicians or even spirits. Making a fake trap that avoiding it in fact triggers a different trap is the most common use. Or just hiding it.

d10 Why did they bother with illusion?1 To hide a trap
2 To act as bait for a trap
3 To scare or warn people
4 To simulate attack or danger
5 To hide a treasure
6 To hide a door or passage
7 To make intruders uncertain
8 As a wacky joke
9 To use as a alarm for locals
10 To act as a test or challenge

d100 Dungeon illusions and phantasms

01 Chattering skulls flies towards intruders laughing 

02 Snakes pour through cracks and cover floor

03 Flies swarm out covering faces and getting in eyes 

04 Swarm of rats panicking

05 Area dripping with slime and dissolved corpses

06 Swarm of bats darken area with chaos

07 Spirits and phantoms swarming everywhere

08 Stirges  swarming hungrily

09 Furious gremlins swarming everywhere 

10 Imps and tiny devils cackling and pointing lewdly scuttling everywhere

11 Explosion of burning flames

12 Arcing bolts of crackling electricity

13 Wall of ice and waves of chilling air

14 Blazing wall of fire blocks area

15 Fog cloud rolls out filling

16 Green vaour pours out and looks toxic

17 Black magical blinding shadows reduces everyone's visibility

18 Bright magical blinding lights reduces everyone's visibility

19 Hail of daggers or darts firing everywhere

20 Swinging bladed pendulums

21 Charging humanoid warriors

22 Huge monster warrior

23 Shield wall of humanoids with spears

24 Dozens of archers

25 Armoured warriors with crossbows and halberds

26 Evil templar warrior priests

27 Robed wizards casting spells

28 Fierce beserkers

29 Armoured warriors

30 Demon or devil 

31 Charging hell hounds

32 Giant frog

33 Giant snake

34 Tentacled horror

35 Gelatinous ooze creature

36 Giant insect  

37 Animated statue or golem

38 Animated floating weapons

39 Elemental being threatens all

40 Roaring dragon breathing fire

41 Stone wall

42 Pit with spikes

43 Burning pit

44 Snake filled pit

45 Mound of rubble

46 Portculis gate

47 Iron bars

48 Heavy door

49 Something ordinary hidden by illusion
50 Something ordinary hidden invisibly
51 Waterfall

52 Boiling water

53 Steam geyser

54 Bubbling pool of acid

55 Pool with swimming monster 

56 Pool with giant octopus

57 Healing spring

58 Well dropping into depths

59 Pool with giant frogs

60 Liquid monster oozes from a vessel
61 Attractive maiden beaconing for help
62 Prisoners bound and moaning
63 Urchins seem afraid and cower in fear
64 Wounded human
65 Pile of gold coins
66 Pile of silver coins
67 Treasure chest open with loot
68 Pile of sparkling gems
 69 Rack of weapons and armour
70 A big black cauldron or stave
71 Piles of barrels of crates

72 Exclusionary light source like candles or fire place

73 Pile of coffins, funerary urns or sarcophagi

74 Pile of old shoes or clothes or old armour from bodies

75 Bundles of firewood or huge oil urns

76 Doors or gates that look functional

77 Trap door or pit or well

78 Pressure plate barely observable

79 Sagging beams or roof as if about to collapse

80 Large egg, possibly about to hatch
81 Piles of rotting corpses
82 Piles of skeletons and bones
83 Piles of desiccated and mummified corpses
84 Piles of gore and offal as if from horrible massacre
85 piles of worm ridden rotting flesh crawling with maggots
86 Horribly tortured corpses in apparatus, crucified or chained up
87 Mounds of skulls heaped in
88 Twitching, bloody and squirming human guts, limbs and other organs
89 Piles of severed heads
90 Piles of eyeballs
91 Magical demonic glyphs appear
92 A magical mouth makes some kind of threat or warning
93 A magical mouth swears, moans or sobs

94 A scream or alarm bell or gong sound that alerts creatures

95 Floating eyeball observing intruders
96 Shimmering gate appears and some planar beings look out
97 Horrible phantom or other impressive looking undead horror
98 Great gate opens and some horrific alien being gazes through
99 Demons or devils torturing victims look gleeful to see fresh victims
100 Illusion of dungeon boss or deity being threatening