24 cards where the card is tagged “demon-synergy”

Aspiring Champion (Warhammer 40,000 Commander #71)
Be'lakor, the Dark Master (Warhammer 40,000 Commander #6)
Blood Speaker (Champions of Kamigawa #103)
Bloodthirsty Ogre (Champions of Kamigawa #104)
Dreadfeast Demon (Innistrad: Crimson Vow #108)
Herald of Slaanesh (Warhammer 40,000 Commander #77)
Inner Demon (Battlebond #48)
Kaalia of the Vast (Double Masters 2022 #235)
Kaalia, Zenith Seeker (Core Set 2020 #210)
Liliana's Contract (Core Set 2019 #107)
Mark of the Oni (Betrayers of Kamigawa #73)
Master of Dark Rites (The Lost Caverns of Ixalan Commander #83)
Ob Nixilis, the Adversary (Streets of New Capenna #206)
Rakdos the Defiler (Dissension #129)
Rakdos, the Showstopper (Ravnica: Clue Edition #205)
Raphael, Fiendish Savior (Commander Legends: Battle for Baldur's Gate #292)
Raving Oni-Slave (Saviors of Kamigawa #86)
Reaper from the Abyss (Commander 2014 #159)
Scroll of Griselbrand (Avacyn Restored #221)
Shadowborn Apostle (Double Masters 2022 #89)
Shadowborn Demon (Magic 2014 #115)
Takenuma Bleeder (Betrayers of Kamigawa #86)
Tiefling Outcasts (Alchemy Horizons: Baldur's Gate #61)
Villainous Ogre (Champions of Kamigawa #148)

Though this query has ended, its relics still slumber in New Argive.