All concepts 
System · Discipline

Umbral

Photometric damping, shadow-scaffold weaving, and the deliberate manipulation of ambient darkness and low-light thresholds to construct physical shrouds, navigate unseen corridors, or cloak material vectors.

The thrill of moving unseen, of weaving shrouds from ambient gloom, and of bending the very absence of light to one's will. It is the power to cloak, to navigate hidden corridors, and to construct tangible forms from shadow.

Books

Harrow the NinthTamsyn Muir
Wooden HeartMartin Day
At the Gates of DarknessRaymond E. Feist
The Ganymede TakeoverRay Faraday Nelson
Salute the DarkAdrian Tchaikovsky
The HeraldEd Greenwood
Mirror sightKristen Britain
VenomJennifer Estep
A Cure for CancerMichael Moorcock
Shadow climberMickey Zucker Reichert
Victory's PriceAlexander Freed
SipBrian Allen Carr
The night clockPaul Meloy
Find Your Own TruthRobert Charrette
CeremonyGlen Cook
SwitchbackMelissa F. Olson
Shoot the MessengerPippa DaCosta
Out of This WorldLawrence Watt-Evans
NomadsBenjamin Kane Ethridge
DichronautsGreg Egan
LightbreakerMark Teppo
Deep TimeTrevor Baxendale
The Return of DaudAdam Christopher
ParallaxJeremy Robinson
LucidOraine Johnson
Ghost DanceChristie Golden
Shadow of HeavenChristie Golden
The MistDean Wesley Smith

Related

ShadowIllusionThe VeilExotic MatterHigh MagicSecrecy Mandate