The idea here is basically a bunch of stuff that damages your opponent upon its death topped off with Torbran and Jaya to deal extra damage, Judith to ping them again and trigger Torbran and Jaya again. Fireblade Artist, Angrath's Rampage, Ayara, and Witch's Oven to get a sacrifice when you need that extra bit of damage from Mayhem Devil (who then triggers Jaya and Torbran again and possibly Judith if it was a nontoken). Rankle and Clackbridge Troll are late additions that I just wanted to test out for the additional sacrifices to fuel Mayhem Devil further...funny that a devil deck includes a way of giving your opponent goats to sacrifice. Spear Spewer and Cult Guildmage are just there for cheap pings (might swap them out for Mayhem Devil or Cauldron Familiar at some point if Spear Spewer and Cult Guildmage don't prove useful). All the tiny token creatures will trigger Cavalcade of Calamity as long as Judith is not on the board, then Cavalcade triggers Jaya and Torbran. Jaya's Greeting, Chandra's Triumph for a more targeted kill. In the most perfect setup, you can drop Massacre Girl to kill off all the cheap devils at once and trigger all the extra damage from Torbra, Jaya, and Judith...it stacks very fast because Judith's extra damage is from her and not from the dead creature so she triggers Jaya and Torbran again which makes each Footlight Fiend or Tibalt's Rager worth a potential 8 damage upon its death. She does not trigger off tokens, so each of Tibalt's devil tokens is only doing 4.
The deck is literal mayhem! Plays exactly how I would expect a Rakdos festival to play! Lots of death, lots of wanting your own stuff to die, lots of craziness.
The mana base is just what I had lying around from the Guild Kit deck and some Dwarven Mines.
Some other interesting bits I was looking at were Ember Hauler and Mask of Immolation, I just like devils more than goblins and attacking more than sacrificing.
Sorry, I like to babble...TL;DR...attack with explodey devils and/or sacrifice them so they damage your opponent when they die. Devils dealing damage and/or dying trigger something for additional damage.