It's a fantasy role-playing game.

DM: You are Vex Vex'ahlia, a half-elf ranger . You are the member of the famous group of adventurers. Previously, The creature in the cell tries to choke out Desmond, but the carriage driver manages to resist. Trinket backs away, taking a hit as he does, then jumps and leaps onto the nearest creature, knocking it prone.
DM: I would say this guy has three-quarters cover, so it would be disadvantage on the attack. You already have disadvantage because it's invisible, so it's hard to hit, regardless.
Player: That was the same one each time. 28.
DM: 28? 28 hits.
Player: Oh, I didn't fucking Hunter's Mark him. God damn it. Fuck. 15.
DM: 15 points of damage. The first arrow sinks into whatever's there, and you can see it jutting out of no physical space.
Player: Now I'm going to Hunter's Mark him and I'm going to hit him again. Can I do that?
DM: Technically, it's part of your attack. You can do two attacks first, then you can bonus action, so you're like (arrow sounds) and then you Hunter's Mark it after.
