Perception

“ Perception represents character's ability to discern objects from far away as well as to notice hidden things in their vicinity. It helps the character to use ranged weapons more effectively, as well as detect hidden objects, passages and creatures. ”

— In-game description

Details

Perception determines your character's overall awareness and effectiveness with ranged weapons. It also affects your character's chance to detect hidden passages, objects or stealthed creatures and NPCs. It does not increase your vision or visible range. Perception does not directly affect your chance to hit, but rather increases your ranged weapon skills, which in turn increases your chance to hit with ranged weapons. Melee weapon hit rate is unchanged but increased with melee skill (through strength or dexterity). No items require perception to be used or equipped.

High perception score is important for characters who wish to use ranged weapons or find traps, stealthed enemies and secrets.

Directly affected skills	Other effects
Guns Crossbows	Detection Finding secrets (uses perception score instead of detection)

Related feats

See Category:Perception feats.

• Snooping increases perception by 3 for the purposes of finding secrets.
• Increased Perception veteran feat increases it by 2.

Related items

Headwear

• Adaptive Goggles (+1 Perception on equip)
• Cyclop's Eye (+1 Perception on equip)
• Synesthetic Refocus (+2 Perception when equipped and character is focused, -2 Perception when character is unfocused)
• Synesthetic Refocus(Hexagon) (+3 Perception when equipped and character is focused, -3 Perception when character is unfocused)
• Metal Helmets (-1 Perception on equip)
• Aegis Sec-trooper Helmet ^E (-1 Perception on equip)
• Praetorian Lawgiver (-1 Perception on equip)
• Gas Mask (-2 Perception on equip)
• Tchortist Bioscrubber (-2 Perception on equip)
• Perceptual Isolation Helmet ^HD (Perception set to 1)

Suit

• Tchortist Noble Robe (-1 Perception on equip)
• Tchortist Rassophore Armor (-1 Perception on equip)
• Biohazard Suit (-2 Perception on equip)
• Fire Proximity Suit (-2 Perception on equip)
• Blast Suit (-2 Perception on equip)
• Robe (-2 Perception on equip)
• Tchortist Robe (-2 Perception on equip)
• Tchortist Vathosphore Armor (-1 Perception on equip)

Food

• All-in (temporarily +3 all base abilities)
• Boolean (temporarily -3 all base abilities)
• Mushroom Salad (temporary +1 Perception)
• Junkyard Surprise (temporary random base ability effect, can only decrease Perception)
• Clean Deal (temporary -1 Perception)
• Mushroom Brew (temporary -2 Perception)
• Kzozel  ^E (temporary -2 Perception)
• Stalagdrop (temporary -1 Perception)
• White Dude (temporarily -2 Perception)
• Cave Tear (temporary -3 Perception)

Drugs

• Third Eye ^E (temporary +3 Perception for the purpose of finding secrets)
• Bioluminous Marsh Honey ^E (temporary +2 Perception)
• Supersoldier Drug (temporary +2 Perception)
• The Juice (temporary +1 Perception)

Perception checks

Discovering secret areas is based on Perception score alone, unlike detecting traps and stealthed characters, which is based on Detection. Discovering some secrets requires prior knowledge instead of Perception score.

In addition to secrets, Underrail: Expedition expansion added visible in-world Perception checks similar to Strength, Dexterity and Agility checks.

Base game

This list is incomplete; you can help by expanding it.

Location	Secret	Requirement	Details
Lower Caves, South Gate Outposts, Area South outposts, inside NW outpost (Forlornstations1.png)	Trapdoor	6 Perception	connects the two south outposts
Lower Caves, South Gate Outposts, Area South outposts, inside NE outpost (Forlornstations1.png)	Trapdoor	6 Perception	connects the two south outposts
Lower Caves, South Gate Outposts, Area East outpost, inside the outpost (ForlornStations4.png)	Trapdoor	7 Perception	connects east and northwest outposts
Lower Caves, South Gate Outposts, Area East outpost, northeast tunnels (ForlornStations4.png)	Trapdoor	8 Perception	connects east and northwest outposts
Under-passages Lower Passages Dungeon, (Dun lup-a.png)	Passage	Quest trigger or 11 Perception	entrance to the next area in the Camera problems quest
Under-passages area 1, near SGS (lup-a1.png)	Door	7 Perception	secret room along east wall, Strange Comm Device oddity
Lower Underrail, GMS compound level 1 (GammaCompound1.png)	Safe	7 Perception	secret safe in room near southwest corner
Lower Underrail, GMS compound level 2 (GammaCompound2.png)	Secret passage	7 Perception	secret room along east wall, Old Data Medium oddity
Lower Underrail, GMS compound level 3 (GammaCompound3.png)	First aid box	7 Perception	SW room, hidden under couch, medicine including an Advanced Health Hypo
Lower Caves, east from GMS compound level 3 (cv12.png)	Secret crawlspace	8 Perception	leads to the back entrance of the raider base
Lower Caves, raider base	Adrenaline shot	8 Perception	under Gerhard Page's bed
Lower Caves between Mushroom Cove and Junkyard (jyt1.png)	Underwater rock bridge	8 Perception	leads to a small island
Lower Caves, Siphoner Pools, northeast (jyt3.png)	Underwater rock bridge	8 Perception	leads to the northeast corner of the cave
Lower Caves, Water Treatment Facility	Plasma cell	6 Perception	under a table in the power room
Lower Caves, Water Treatment Facility	Shotgun shells	8 Perception	on top of a locker in the SE room on the upper level
Lower Caves, Water Treatment Facility	First-aid kit	7 Perception	in the SE room on the lower level, random medicine
Lower Caves, Water Treatment Facility	Hidden opening	9 Perception	secret compartment in the ventilation system, Deathstalker corpse with Crawler's Eye oddity
Lower Caves, Water Treatment Facility	Secret crawlspace	7 Perception	along north wall on the lower level, leads to secluded room with loot
Silent Isle, southeast (si1.png)	Underwater rock bridge	7 Perception	leads to a small island with a corpse with random Mutated Dog Leather Armor
Junkyard, Security control room of Depot A east area (ojy2.png)	Secret door	10 perception	shortcut bypassing the turrets
Lower Underrail area 6, Lunatic camp (lu-a6.png)	Hidden stash	8 Perception	secret footlocker near rock pile
Upper Caves, south of Milton's camp (lux-a10.png)	Underwater rock bridge	7 Perception	shortcut between the north and south bank of the river
Upper Caves, ironhead camp, two zones north of the Bunker (Lux-b16.png)	Hidden stash	10 Perception	NW corner of map, through the backside of the camp, contains a Jumping Bean and random tabi boots
Upper Caves, Synesthete camp, under the Oculus	Hidden stash	11 Perception	in the rock next to the Synesthete, contains roughly 300 charons
Upper Caves, misty river north of Hecate caves entrance	Underwater rock bridge	9 Perception	leads to a box containing a Niobium Piercing Set
Lost Vault entrance	Hidden ventilation shaft	9 Perception	leads into the shack behind the trader
Lost Vault interior	Hidden first-aid box	7 Perception	random medicine
Lost Vault interior	Hidden footlocker	7 Perception	in room along north wall, contains Circular Wave Amplifier
Lost Vault interior	Hidden bag	10 Perception	in the northern room along west wall, accessible only with 11 Strength, contains two advanced mechanical and electronic repair kits and a lighter
Lost Vault interior	Hidden sack	9 Perception	South-western room, accessible only with 11 Agility, contains Greater Fusion Cell, two Fusion Cells and two Plasma Cells
Lower Caves, south of Crossroad Caves (cv2.png)	Trapdoor	8 Perception	connects southwest and southeast corner, locked box with random psionic mentor
Lower Caves, south of Crossroad Caves (cv2.png)	Underwater rock bridge	7 Perception	shortcut bypassing siphoners
Lower Caves, south of Camp Hathor (cv19.png)	Underwater rock bridge	7 Perception	shortcut bypassing rathound nest
Lower Caves, Rathound King Lair (rkl2.png)	Door	Quest trigger or 10 Perception	shortcut leading outside if you offer to kidnap Sarine or negotiate a truce with Camp Hathor
Lower Caves, Rathound King Lair, outside (cv21.png)	Door	Quest trigger or 15 Perception	shortcut leading to the lair if you offer to kidnap Sarine or negotiate a truce with Camp Hathor
Lower Underrail, Abandoned Warehouse (aw1-1.png)	Secret crawlspace	7 Perception	secret ventilation shaft section with a footlocker and a rathound
Rail Crossing, behind bar (rc1.png)	Secret door	7 Perception	leads to Deacon's shop
Rail Crossing, Buzzer's Shop's ventilation shafts (rc_shop 3.png)	Hidden Ventilation Shaft	7 Perception	secret ventilation shaft section with Hardware Bug
Lower Underrail, The warehouse from Dude's vision (lu-b4.png)	Secret crawlspace	Quest trigger	leads to the lower level of the warehouse during Dude's quest
Free Drones Base, east room	Trapdoor	11 Perception	can't be opened; handle breaks
Upper Caves, north from the Hanging Rat bar (lux-c2.png)	Hidden stash	11 Perception	secret stash inside rock pillar (not visible on the linked map)
Foundry, Evelyn's home (fo3.png)	Trapdoor	10 Perception	connects Evelyn's house and bunker
Foundry, Evelyn's home (fo3.png)	Secret crawlspace	Quest trigger	leads to Evelyn's bunker if a male player character has a drink with her
Lower Underrail, cave west of Foundry (lu-b22x.png)	Hidden stash	10 Perception	secret stash inside rock pillar
Core City, SW middle level (Cc17.png)	Ladder	14 Perception	leads to Phreak's hideout, utility section electric coil area
Core City, utility section (Cc_utility.png)	Squeeze through gap in pipes	11 Perception (can be bypassed with night vision mode of the Goggles)	leads to Phreak's hideout, boilers area
Core City, Utility Facility steam area	Junk pile	7 Perception	Contains TiChrome Spikes and a Boot Spring, NW corridor
Core City, Utility Facility steam area, through the door east of the steam console, near Modified Industrial Bot	Plasma cell	10 Perception	Plasma Cell and a Plasma Core
Core City, Utility Facility electric coil area	Phreak's laptop	Quest trigger	laptop hidden in trash pile in his hideout, available after his disappearance
Core City, Utility Facility electric coil area, SE room on 2nd floor	Bag	8 Perception	random knife
Core City, Drop Zone (cc15.png)	Secret door	Quest trigger or 6 Perception	leads to Bogdan's hideout, can be found with perception or by learning about it from Kupusije during Find Bogdan, or with perception after starting Sewers generator/Retrieve ICPD
Core City, inside one of Drop Zone buildings (cc5_1.png)	Trapdoor	8 Perception	leads to the basement
Core City, north Core City Sewers (cc_s2.png)	Door	8 Perception	leads to a secret room on the west side containing some loot
Core City, northwest Core City Sewers (cc_s6 2.png)	Switch	Quest trigger	opens door to Acid Hunters' hideout during the Look for Cornell quest
Core City, Zaman's Lair, Underground lake (Cc zamanscave2.png)	Hidden stash	9 Perception	contains around fifty UN dollars
Core City, Port Zenith warehouses	Hidden safe	9 Perception	Hidden locked safe in Captain Wilkinss room, contains fifty United Stations Dollars, an energy pistol and a Fusion Cell
Upper Underrail, east of Notus Living Block (up3x.png)	Trapdoor	7 Perception	connects trapdoor and a Lunatic base
Upper Underrail, inside Panacea Lab (plb.png)	Switch	8 Perception	opens door to the room in the northeast corner
Upper Underrail, Gubbins' banidt camp (Up7.png)	Ventilation Shaft	8 Perception	connects inside of structure to outside, north of the barrel fire
Utility Tower, first room past metal gate	Ventilation Shaft	9 Perception	ladder leading up, skips some floors
Institute of Tchort, armory, behind the locked fence (Tch-mil.png)	Box of ammo	8 Perception	x11 12.7mm W2C Rounds
Institute of Tchort, utility section 2, south room (Tch-util2.png)	Box	8 Perception	one Aegis, three Gizzard Enzymes
Institute of Tchort, utility section 3, northwest corner (tch-util3.png)	Morphine shot on file cabinet	10 Perception	one morphine shot
Institute of Tchort, utility section 3, northeast corner (tch-util3.png)	Ventilation Shaft	8 Perception	connects west wing and utility section
Institute of Tchort, west wing, in coil spider room (tch-ww2.png)	Ventilation Shaft	7 Perception	connects west wing and utility section
Institute of Tchort, Harpocrates Station, north room (tch_met.png)	Secret crawlspace	Quest trigger	leads to the ventilation system during Track down Rassophore Nevil
Institute of Tchort, Upper Underrail Ventilation System (tch_mv1.png)	Secret crawlspace	8 Perception	secret ventilation shaft section with a box
Institute of Tchort, Upper Underrail Ventilation System, southwest room (tch_mv1_2.png)	Secret trapdoor	10 Perception	leads to hidden basement
Deep Caverns, lake, northeast bank (dc-lk.png)	Underwater rock bridge	7 Perception	leads to a small island with hackable box
Deep Caverns, lake, southwest islet (dc-lk.png)	Sniper rifle	10 Perception	reveals Black Arrow sniper rifle
Deep Caverns, Hollow Earth (dc-la2.png)	Secret crawlspace	8 Perception	secret entrance to the small building on the east
Deep Caverns, checkpoint between Caerus and warehouses (dc-cp1.png)	Underwater rock bridge	8 Perception	leads to the east bank of the lake
Deep Caverns, Warehouse Block 2, south toxic storage (dc-wh3.png)	Trapdoor	8 Perception	leads to lower level, Electrokinetic Imprint mentor
Deep Caverns, Caerus Residential, northwest building, second floor (dc-res2 2.png)	Ventilation Shaft	10 Perception	leads to a cavern with Gunter Vasilica, Pseudo-spatial Projection mentor, and Regenerative Mixture
Deep Caverns, Caerus Residential, west apartment (dc-res3.png)	Safe	6 Perception	secret safe
Deep Caverns, Arke Power Station, utility section toxic storage (dc-pp_ut.png)	Trapdoor	11 Perception	connects toxic storage and storage room
Deep Caverns, Arke Power Station, utility section storage room (dc-pp_ut.png)	Trapdoor	10 Perception	connects toxic storage and storage room
Deep Caverns, Deep Mushroom Forest (dc-fs4.png)	Secret tunnel	9 Perception	leads to the northwest corner and a skeleton

Expedition

This list is incomplete; you can help by expanding it.

Location, Underrail	Secret	Requirement	Details
Abandoned Waterway Facility, east zone, on the island south of the bridge	Hidden stash	8 Perception	exceptionally high-quality Mutated Dog Leather
The Rig, room #2	Note (The Rig)	5 Perception	under the bed
Rig Periphery, Waterways 9	Hidden stash	Quest trigger or 16 Perception	discovers Knuckles' stash
Chancer's Bay, NE map	Hole through wall of shack	10 Perception	biohazard boots, corrosive acid, Encyclopedia Fragment oddity, mutants
Isaac's River, northernmost map	Hidden stash	10 Perception	stash in north wall of cave
Core City Docks, empty room next to Ray's shop	Vent in north wall	10 Perception	leads into Ray's shop, dying burglar
Dude's House - Core City	Cracked floor panel/wall safe	5 Perception	key to wall safe/the safe itself
Dude's House - Caves	Footlocker under bed	9 Perception	psionic mentor
Gray Army Base - Barracks, two rooms east of the rift	Secret trapdoor	8 Perception	electronic components
Gray Army Base - Schtab	Wall safe	9 Perception	secret safe in north wall of northwest room
Gray Army Base - Schtab	Secret opening	9 Perception	Connects northern and southern parts of the ventilation system

This list is incomplete; you can help by expanding it.

Location, Black Sea	Secret	Requirement	Details
Black Sea (E4), north side of island	Entrance to cave	11 Perception	entrance to pirate prison trash dump, leads to Thrasher, a boss hermit crab
Siphoner Pools (Black Sea)	Underwater rock bridge	7 Perception	leads to a lingula plant and a random treasure "crevice"
Siphoner Pools (Black Sea), west chamber	Buried box	11 Perception	SGS credits, Charons, US dollars
Black Sea (C8), hopper island cave, north wall, west side	Hidden stash	9 Perception	secret stash in cave wall, Bolt Quiver and some special bolts
Black Sea Grotto (A10), Yngwar's cave island, hidden walkway in water on east side	Hidden stash	8 Perception	secret stash in cave wall, contains coagulation shot, two antidotes and four rusting acid cvials
Mutie Refuge, crane room	Hidden vent shaft	7 Perception	secret vent shaft through wall into crane room
West Storage Depot, lvl 2, east room	Hidden box of bullets	6 Perception	30x 9mm Standard Rounds
West Storage Depot, lvl 2, southeast room	Hidden box of bullets	9 Perception	11x 12.7mm Standard Rounds
West Storage Depot, lvl 3 by the elevator	Hidden vent shaft	8 Perception	secret vent shaft to blocked room
Crimson Meadow Horticulture Center lower floor, west section, north side	Hidden vent shaft	11 Perception	secret vent shaft through wall
Black Sea (I1), outside the Health Center, SE corner	Hidden hole through wall	10 Perception	secret passage to hidden room
Black Sea (I2), tower north of Health Center, 2nd floor	Hidden corpse	9 Perception	corpse with loot (can be looted without detection)
Nexus of Technology, level 1, SE room	Hidden wall safe	9 Perception	safe contains Energy Shield Emitter and two Plasma Cells
Port Crag, east building	Hidden pipe tunnel	9 Perception	drawl through to west building, 2nd floor (agility 8; it is from the other direction)
Fetid Marsh, east side of K5/west side of L5	Hidden map exit(s)	10 Perception	secret camp with Signed Arena Ticket and "ArenaNow" Broadcasting Schedule oddities and Slimy Tablet Computer
Fetid Marsh, SW corner of K4	Hidden pool jumps	12 Perception	secret platforms for easier jumping across leper pool
Giant Creeper Lair (two maps east of the Nexus), NW corner	Hidden passages	9 Perception	secret passages to/from hidden room, shortcut past creepers

Heavy Duty

This list is incomplete; you can help by expanding it.

Location	Secret	Requirement	Details
Core City, Rag's Boutique	Hidden trap door	11 Perception	Discover entrance to the basement
Core City, Rag's Boutique, basement	Discover contents behind the curtains	13 Perception	Allows to target the auto-turrets without lifting the curtains
The Compound, outside, northern side of the map	Hidden metal plates	10 Perception	Hidden high quality two random metal plates behind a fence
The Compound, entrance stairs	Hidden vent	14 Perception	Leads to a blocked restroom that has a medical locker with Adrenaline Shot and Coagulation Shot
The Compound, entrance offices	Hidden safe	12 Perception	Hidden locked safe containing around 100 charons and a Gold Ring
The Compound, exoskeleton assembler lab	Shelf back panel missing	15 Perception	Secret passage behind a computer rack to the north, leads to a box with 3 Shock Bolts Mk III, 2 Plasma Grenades Mk III and a Laser Pistol
The Compound, Fusion Cannon lab	Hidden Plasma Cell	9 Perception	Under a table in the south
The Compound, medical section 1	Smaller box	12 Perception	Hidden box inside a bigger box in the office, contains a vial of Aegis
The Compound, medical section 2	Super Health Hypo	11 Perception	Found under a desk near the med stations in eastern side of the map
The Compound, command, NW room	Hidden safe	14 Perception	Hidden locked safe containing 3 Fusion Cells, 3 Shock Bolts Mk III, 4 Shock Bolts Mk II and a high quality Smart Module