Nightengale

You are a trained assassin who specializes in appearing and disappearing within a flash, unnoticed, unseen and unheard. When you take this feat you gain the following benefits.

• When you are in cover and within 10 feet of a target, the DC for stealth checks is 5 points lower than normal and you can use your cover to successfully travel between shadows, unseen, as long as nothing is illuminating those shadows. 
• You have advantage on rolls to check the contents of someone's pockets without alerting them to your presence, as long as you don't remove anything from their pockets or backpacks. 
• You can easily memorize your marks frequented locations and known associates, as with the keen mind feat, and roll with advantage on insight checks when it comes to remembering them within 30 days. 
• You have advantage on medicine checks to tell how long blood or a corpse has been somewhere based on how dry or wet the blood is or the state of decay.