3-6 player multiplayer

All normal commander rules entirely unmodified EXCEPT

100 starting life

20 card deck

Each player starts with a Descent into Avernus in play that cannot leave the battlefield

Don't bother with lands

Yeah.

(There's also a fairly intuitive tiebreak rule. The player with the most life after all remaining players lose simultaneously due to have 0 or less life wins the game rather than a draw occuring. Essentially this makes it so when an Avernus trigger kills everyone, the player you'd expect to win does, but that's not punchy.)