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)
• 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

• Mushroom Salad (temporary +1 perception)
• Junkyard Surprise (temporary random base ability effect, can only decrease Perception)
• Mushroom Brew (temporary -2 perception)
• Kzozel  ^E (temporary -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

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 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 Caves, east from GMS compound level 3 (cv12.png)	Secret crawlspace	8 Perception	leads to the back entrance of the raider base
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
Silent Isle, southeast (si1.png)	Underwater rock bridge	7 Perception	leads to a small island with a corpse
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
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	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	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	leads to the ventilation system
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, 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
Institute of Tchort, utility section, 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	Secret	Requirement	Details
The Rig, room #2	paper note	?	under the bed
Chancer's Bay, NE map	hole through wall of shack	?	biohazard boots, mutants
Isaac's River, northernmost map	hidden stash	?	stash in north wall of cave
Empty room next to Ray's shop, Core City docks	vent in north wall	?	leads into Ray's shop, dying burglar
Dude's old house in Core City	cracked floor panel/wall safe	?	key to wall safe/the safe itself
Dude's cave house	footlocker under bed	?	psionic mentor
Grey Army Base, 2nd floor	wall safe	?	secret safe in north wall of northwest room