Eberron - A New Era
The Mark of Detection grants abilities that enable its possessor to discern the presence of threats, from poisoned food to scrying eyes.
House: The half-elves of House Medani carry the Mark of Detection.
Marks: The aspects of the Mark of detection carry the following benefits.
Least Mark of Detection: detect magic 2/day or detect poison 2/day; you are proficient in Perception. If you are already proficient in Perception, you gain advantage in Perception checks.
Lesser Mark of Detection: detect scrying 1/day or see invisibility 1/day.
Greater Mark of Detection: true seeing 1/day.