Rakdos Sacrifice is a powerful and fun synergistic deck that has been around since Throne of Eldraine. Theros Beyond Death gives it some nice new tools in the form of Woe Strider and Blood Aspirant.
Rakdos Sacrifice with Theros Beyond Death
4 Gutterbones 4 Cauldron Familiar 4 Witch's Oven 4 Claim the Firstborn 4 Priest of Forgotten Gods 4 Blood Aspirant 1 Lazotep Reaver 2 Judith, the Scourge Diva 4 Mayhem Devil 3 Woe Strider 3 Midnight Reaper 4 Temple of Malice 4 Fabled Passage 5 Mountain (343) 1 Castle Locthwain 5 Swamp (339) 4 Blood Crypt
Arena-Formatted Decklist - Rakdos Sacrifice 4 Cauldron Familiar (ELD) 81
5 Swamp (ANA) 63
4 Priest of Forgotten Gods (RNA) 83
2 Judith, the Scourge Diva (RNA) 185
4 Blood Aspirant (THB) 128
5 Mountain (ANA) 64
4 Mayhem Devil (WAR) 204
3 Woe Strider (THB) 123
4 Claim the Firstborn (ELD) 118
1 Castle Locthwain (ELD) 241
4 Witch's Oven (ELD) 237
4 Blood Crypt (RNA) 245
4 Temple of Malice (THB) 247
4 Fabled Passage (ELD) 244
1 Lazotep Reaver (WAR) 96
3 Midnight Reaper (GRN) 77
4 Gutterbones (RNA) 76
4 Cauldron Familiar (ELD) 81
Woe Strider is an amazing pickup for this strategy. Unfortunately this deck is already glutted at three mana, but this card is certainly worth the slot. It provides us a "hasty" and unlimited sacrifice outlet, which also helps us filter through our synergistic deck to find the right pieces. It also provides two bodies at a good rate, and can even be cast a second or third time later in the game for value. This is just a pushed cart that happens to do a bit of everything that we are looking for.
Blood Aspirant is the other key addition to this deck from Theros Beyond Death. Having a second card that has the actual text found on Mayhem Devil means we have twice as many opportunities to take advantage of all the sacrificing we were already planning to do. This creature is easily a 6/6 or larger for just two mana, eerily resembling Ajani's Pridemate out of the Mono White Devotion Lifegain deck. It's just a bonus that it has its own sacrifice clause, which can either shoot down something like a Paradise Druid or just get your sacrifice gears spinning if you don't have access to another. The ability to remove a blocker is rarely useful since the Apirant will likely be your largest attacker anyway, unless the opponent would be able to block with a lifelink creature.
For our 1-drops we're just running four copies of the staples for this archetype. Claim the Firstborn is incredible as a one mana removal spell that can fuel all of our sac outlets and do some extra damage. One tip to note is that it can also give our own Blood Aspirant haste for a burst of damage to finish the game or kill a planeswalker. Witch's Oven and Cauldron Familiar is an old favorite that is good in a lot of decks but even better in this one. Our last 1-drop creature of choice is Gutterbones, as it is the best at getting in some chip damage and can be easily recurred later in the game. Footlight Fiend is another option if we want to lower our curve even more, but it shouldn't come in before any of these 16 cards.
Priest of Forgotten Gods is our only other 2-drop, and it helps up our count of "must kill on sight" type creatures that overload any opponent playing point removal. Notably, we are excluding Dreadhorde Butcher, which has typically been a staple in this style of deck. While Dreadhorde Butcher is a powerful card that fits well into this archetype, it can often be very weak on the draw or against opponents who can clog the board. With the increased power level of this deck due to the new cards, we're opting for a more consistent approach. For this reason, we are also eschewing any copies of Lazotep Reaver. By omitting these situational cards, our entire deck is filled with only cards that are of a high power level and contribute directly to our key synergies in every game.
Finally, we have the wonderful 3-drop slot. Mayhem Devil is of course the main reason we are even playing this strategy. After that, we still want to cram in some copies of Judith, the Scourge Diva and Midnight Reaper. Both of these creatures are obviously extremely powerful within this context, but we personally err towards the side of playing higher numbers of Midnight Reaper. In a synergy-based deck, you generally win when you can assemble all the pieces of your engine, so having access to more card draw is always welcome. In further tuning of this deck, the goal will be to determine just how many of these amazing 3-drops we can fit into the deck before we've done damage to our curve.
We would be remiss if we didn't mention these two important lands. Fabled Passage is of course a decent mana fixer that also now directly triggers 8 of our cards. It also helps fill the graveyard to fuel Woe Strider. Temple of Malice is a very welcome addition from Theros Beyond Death, as the heavy colored mana requirements combined with the lack of this Temple was one of this deck's biggest weaknesses in the previous format.