Make players locked to the dungeon once the first Headless Horseman is killed

If players in a group kill at least one Headless Horseman, give them an ID and prevent them from entering another group. Instead, redirect them to the regular version of the dungeon, which has no pumpkin that's needed to summon the boss.

I am suggesting this change to prevent players from abusing the system by leaving their group and joining another one without summoning the Headless Horseman themselves.

The ID would reset every day.