Let me just begin by saying that this was my first time ever DMing a series of sessions. The sessions I headed were branched off from our main campaign, where 4 characters from the party ventured off to get supplies from a village and were sealed inside because of a plague that popped up overnight.
The first two sessions were great–no one suspected what I was doing, the players were making mediocre rolls. Basically, most everything was going to plan.
We were relaying what had happened in the first two sessions to another player when he said, “I want to join the next session!”
This player is the DM of our main campaign. This should have been a red flag to me. But no. I had to be Mrs. Nice Guy and say, yeah, I could incorporate his character into the next session. It would be great fun, I thought to myself.
We will refer to this person as Diablo, one reason because that is what we call him, and the second reason because after this experience i truly saw Lucifer in his eyes.
I successfully get his character into the quarantined village, he reunites with his party members, and together they all find out that the village had been cursed by a devil worshiper and they had to find out who the person was.
This is when I realized I had made a mistake.