shadowoflameth
Adventurer
If you are willing to convert a creature to 5E, back in 4e was the Gremlin. There was one that became invisible when an enemy was adjacent to it. I had the as guards once and the rogue snuck up on them. Whoops.
Always an option of course, but its nice to know what the raw material is before I start messing with the clay.But... you're the DM.
Pick any monster. Give it profiency in perception. Expertise even. It's been specially bred (or recieved the appropriate training).
Always an option of course, but its nice to know what the raw material is before I start messing with the clay.