The easiest way to evaluate new cards is to refer to an older card that’s similar. Unless you started playing Magic very recently, Hero’s Downfall was the first card you thought of when Bedevil was previewed.
Hero’s Downfall was format defining. Every black deck played it. Some decks played black just for Downfall, and it even saw a bit of play in Modern. I personally liked it in both Faeries and Blue-Black Midrange—it filled a hole no other card could.
Unless Rakdos gets no other good cards outside of Rix Maadi Reveler, Bedevil will see play in Standard. Even if Rakdos is bad, with all the good dual lands, I can see people splashing for it.
Bedevil can hit artifacts, and that’s the part of the card I want to analyze—we already know the Hero’s Downfall part is great.
Treasure Map is the most important target for our new versatile artifact removal spell. Map has started seeing lots of play in many different decks, and Grixis or Dimir splashing will gladly add this to now have an answer to it. Golgari is probably the deck most likely to splash for Bedevil, and between Blood Crypt, Stomping Ground, and explore creatures, it might outweigh the downside of Assassin’s Trophy.
The Immortal Sun saw play over the past few months as a counter to the planeswalker build of Golgari. If that happens to be the case again, then it’ll want Bedevil even more.
Sorcerous Spyglass does not see a lot of play, but I expect that to change because of the printing of Hallowed Fountain, and Teferi, Hero of Dominaria is such a powerful card. Maybe there will be a great red-black planeswalker, and then Bedevil will be useful for killing this artifact.
Azor’s Gateaway saw a little bit of play thanks to Expansion // Explosion, but ultimately people stopped playing it. In my opinion, it was too clunky and slow for the format. I don’t expect that to change.
Maybe there’s a world you can still play Llanowar Elves in this, but I don’t want to live in that world. Banefire, Lava Coil and Dire Fleet Daredevil are reasonable options if you want to play some red.
More often than not, versatile removal spells really shine in Modern because there are so many different decks you need answers to. I think Bedevil is a bit too expensive to make it see drastically more play than Hero’s Downfall, and it is likely worse than Kolaghan’s Command for decks that can cast red-black cards.
Grixis decks that play Cryptic Command certainly can’t cast BBR.
Hollow One already has Ancient Grudge, which is a much better card in that deck with all the looting.
Jund already has tons of other artifact answers thanks to the green.
Do you see where I’m going with this? Unfortunately, I don’t see Bedevil outclassing anything we already have in Modern. Hero’s Downfall saw play specifically in blue-black decks because they don’t want to splash another color, often because of Cryptic Command.
The list of what it kills is long, but it’s hard to cast and costs 3 whole mana. Plus, it does not seem to fill holes that any archetype was lacking.
It’ll still be great for Standard, just like Hero’s Downfall was, but the added artifact clause is not groundbreaking by any means.