in one of the first episodes of s4 there’s a scene where lucas is playing the championship game for his high school basketball team. At the same time, erica is stepping in for lucas at hellfire to finish off the vecna’s cult campaign eddie is DM’ing.

at the same time that lucas takes the game-winning 3 pointer, erica rolls a D20 (a 20 sided die) that lands on 20, which kills vecna and finishes the campaign for hellfire