I was DMing a session with a group of friends when this situation occurred. One of the PCs was near a hydra and he used his bonus action to disengage from it after attacking it. He can do so because of his rogue ability called cunning action.
How do opportunity attacks work for a monster like the hydra? The hydra has an ability called Reactive Heads which makes it use as many reactions as it has heads. The hydra had 4 heads at the time. I don't understand how it works in this situation. Does the rogue get away safely even though the hydra has more than 1 reaction? How does the disengage action work against a hydra or any monster with the reactive heads ability?