It's a fantasy role-playing game.

DM: You are Vax Vax'ildan, a half-elf rogue . You are the member of the famous group of adventurers. Previously, As they move through the city, the group encounters clusters of undead from two factions: one wearing symbols of Pelor, the Dawn Father, while the other faction seems to be associated with Vecna. you, looking more closely at a group of skeletons as they pass, determines they must be at least 500 years old.
DM: With the brief glances you have, it's hard to really tell. Plus, you're not too familiar with the overall weather of the Shadowfell. You don't know if there's enough weather to manifest as general decay, or if they've been beaten by the ravages of time, if it rains here or not. It's hard to tell. You gather it probably doesn't rain often. They're definitely hundreds of years old. That's the most you can really tell. They aren't fresh dead. These are long dead.
Player: I'm feeling Foresighty. Can I creep up behind and do the same?
DM: I will say you can do that, however you still have disadvantage, because she's already taken the roll and you're supplementing her roll in a very short period of time.
Player: Would that be an even roll, then, since I have advantage on everything?
DM: You have advantage on everything. I'm giving you a chance to do this when normally you would have none, so the Foresight's allowing you to have a roll with disadvantage. Go for it.
Player: Oh, that's going to fail. Ooh! 18.
DM: Or not. Getting a glance at the one nearest to you, the bodies seem to be fairly well preserved for as long as they've been here, so you get the sense that there isn't a lot of heavy weather here at all. And given that fact, the decay that's there, it is reminiscent, maybe not quite as old as the corpse of Purvon when you discovered the tomb originally, but comparatively ancient. At least over 500 years.
