When I was a teenager playing Advanced Dungeons and Dragons, we had a rule that we made up about rolling a 20 to hit. If we rolled a 20 to hit, we did double damage and we could roll again. If we rolled another 20, we tripled the damage and rolled again. If we rolled a third 20, the target died instantly.
I was playing a wizard and I think we were about 8th level. We were pretty beaten up and locked in an encounter with a T-Rex type creature with a rider. I didn't have many spells available so I just threw a dagger at the T-Rex....20, 20, 20! Everyone went wild as the dagger went into the creature's eye and killed it outright. It fell to the ground and the rider fell as well. I can't remember if the rider died or if we just finished him off, but that was a memorable event in our campaign.
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Here's another one about how I actually started in my first campaign. -
A friend of mine told me that he was playing in someone's campaign. The DM was a few years older than I was and I didn't really know him. My friend told me to come to the DMs house and he'd introduce me and get me into the game. Well, I was a shy kid so when I went over to the house at about 8 or 9 ish at night, I saw that the house was dark, except for a light in one of the rooms on the 2nd floor in the back of the house. I assumed that that was the room they were playing in so I grabbed some pebbles and small sticks, and I tried to throw them up at the window to get anyone's attention. I must have spent nearly 30 minutes trying. Eventually, someone heard me and I got to join my first campaign. That was over 38 years ago. I ended up becoming really good friends with the DM and others in the group, and many of us are still friends today (even though we don't live near each other any more).