It's a fantasy role-playing game.

DM: You are Mollymauk Tealeaf, a tiefling blood hunter . You are the member of the famous group of adventurers. Previously, Wary of its toxins, they all stay out of melee range. When the troll gets to its feet, it moves closer to Beau and Yasha, hitting them both with its poison spray and poisoning Yasha, but she shrugs it off at the end of her turn.
DM: As you carve past, with a third, final swing towards it, you cut through a portion of muscle and tendon on its arm there, which immediately slips, dull to one side, unmoving. The spray splashes back in your face for only five points of poison damage. And it's coming into you. As soon as that arm goes limp, the muscle reconnects and the arm comes back with strength, angrily. It's going to swing. It's going to take a bite and two claw attacks against you.
Player: He's also going to, of course, Curse of the Eyeless.
DM: You can't. You already used your reaction to attack him.
Player: Oh, that was my reaction. Never mind.
DM: Sorry, buddy.
Player: That's all right.
DM: For its bite attack against you, its jaws open, Fjord. That is going to be a 26.
