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)
• 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)

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)
• Robe (-2 Perception on equip)
• Tchortist Robe (-2 Perception on equip)

Food

• All-in (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)
• White Dude (temporarily -2 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	? Perception	under 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	? Perception	under a table in the power room
Lower Caves, Water Treatment Facility	Shotgun shells	? Perception	on top of a locker in the SE room on the upper level
Lower Caves, Water Treatment Facility	First-aid kit	? Perception	in the SE room on the lower level, has antidotes
Lower Caves, Water Treatment Facility	Deathstalker corpse with oddity	? Perception	in a secret compartment in the ventilation system
Lower Caves, Water Treatment Facility	Hidden vent shaft	? 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, north of the Bunker (Lux-b16.png)	Hidden stash	? Perception	NW corner of map, through the backside of the camp, a jumping bean and tabi boots
Upper Caves, Synesthete/Formedicator camp, under the Oculus	Hidden stash	? Perception	in the rock next to the Synesthete, 293 charons
Upper Caves, misty river north of Hecate caves entrance	Hidden box	? Perception	contains a luxury item
Upper Caves, Lost Vault entrance (Lux-b9.png)	Hidden ventilation shaft	? Perception	leads into the shack behind the trader
Upper Caves, Lost Vault interior	Hidden first-aid box	7 Perception	random medicine
Upper Caves, Lost Vault interior	Hidden footlocker	? Perception	in room along north wall, electronic component(s)
Upper Caves, Lost Vault interior	Hidden bag	? Perception	in room along west wall, advanced repair kits & a lighter
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 ? 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 utility section electric coil area
Core City, utility section (Cc_utility.png)	Squeeze though gap in pipes	? Perception	leads to Phreak's hideout
Core City, utility section steam area	Junk pile	? Perception	mechanical components (probably randomized), NW corridor
Core City, utility section steam area	Plasma cell	? Perception	hidden plasma cell, through the door east of the steam console, along the south wall
Core City, utility section electric coil area	Phreak's laptop	? Perception	laptop hidden in trash pile in his hideout, available after his disappearance
Core City, utility section electric coil area	Bag	? Perception	knife (probably randomized), SE room on 2nd floor
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
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
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, northeast corner (Up7.png)	Ventilation Shaft	? Perception	connects inside of structure to outside, north of the barrel fire
Upper Underrail, utility tower, first room past metal gate	Ventilation Shaft	? Perception	ladder leading up, skips some floors
Institute of Tchort, armory, behind the locked fence (Tch-mil.png)	Box of ammo	? Perception	x11 12.7mm WC
Institute of Tchort, utility section 2, south room (Tch-util2.png)	Box	? Perception	one aegis, three gizzard enzymes
Institute of Tchort, utility section 3, northwest corner (tch-util3.png)	Morphine shot on file cabinet	? 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 (empty) safe
Deep Caverns, Arke Power Station, utility section toxic storage (dc-pp_ut.png)	Trapdoor	11 Perception	connects toxic storage and storage room, random psionic mentor
Deep Caverns, Arke Power Station, utility section storage room (dc-pp_ut.png)	Trapdoor	10 Perception	connects toxic storage and storage room, random psionic mentor
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	? Perception	exceptionally high-quality mutated-dog leather
The Rig, room #2	Note (The Rig)	5 Perception	under the bed
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	?	leads into Ray's shop, dying burglar
Dude's House - Core City	Cracked floor panel/wall safe	?	key to wall safe/the safe itself
Dude's House - Caves	Footlocker under bed	9 Perception	psionic mentor
Grey Army Base, two rooms east of the rift	Secret trapdoor	8 Perception	electronic components
Grey Army Base, 2nd floor	Wall safe	9 Perception	secret safe in north wall of northwest room
Grey Army Base, 2nd floor	Secret crawlspace	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 sewer, 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, UN dollars
Black Sea (C8), hopper island cave, north wall, west side	Hidden stash	9 Perception	secret stash in cave wall, quiver belt and special bolts
Black Sea (A10), Yngwar's cave island, hidden walkway in water on east side	Hidden stash	? Perception	secret stash in cave wall, coagulation shot(s) and rusting acid chemical ammo
Mutie Refuge, crane room	Hidden vent shaft	7 Perception	secret vent shaft through wall into crane room
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	loot
Port Crag, east building	Hidden pipe tunnel	9 Perception	Crawl 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 Oddity and Slimy Tablet Computer
Fetid Marsh, SW corner of K4	Hidden pool jumps	12 Perception	secret platforms for easier jumping across leper pool
Map M7 (two maps east of the Nexus), NW corner	Hidden passages	9 Perception	secret passages to/from hidden room, shortcut past creepers