I'm playing a Halfling Gloomstalker Ranger in my game. One of the players just rerolled their character as a Drow. My character is level 4, so he has the class feature Umbral Sight which reads as follows
At 3rd level, you gain darkvision out to a range of 60 feet. If you already have darkvision from your race, its range increases by 30 feet.
You are also adept at evading creatures that rely on darkvision. While in darkness, you are invisible to any creature that relies on darkvision to see you in that darkness.
My question is specifically how to play out the mechanic of my character's disappearance in front of my party member.
This is brilliant! But yeah, it is "creepy" just disappearing on your friends, but it seems to be RAW. However, Mike Mearls replied to a tweet about it: "I believe you can always choose to make yourself visible to a creature"
Of course I somehow missed any notifications for this. So far we've been playing it as though I just disappear in front of them, but we could make it so my character figures out how to make myself purposely visible to anyone of my choice as though I learned how somehow